Ink for ink jet recording, process for the production of ink and ink jet recording process

ABSTRACT

An ink for ink jet recording having a phthalocyanine dye dissolved and/or dispersed in an aqueous medium, characterized in that the aforementioned phthalocyanine dye is a water-soluble dye having an oxidation potential of more positive than 1.0 and the conductivity of the aforementioned ink is from not 0.01 S/m to not greater than 10 S/m. A process for the production of the aforementioned ink for ink jet recording which comprises a step of applying ultrasonic vibration and/or a step of filtering using a filter having pores of an effective diameter of not greater than 1 μm and defoaming the ink and an ink jet recording process using these inks. In accordance with such a constitution, an ink for ink jet recording and an ink jet recording process can be provided which exhibit a high ejection stability, give an image having an excellent hue and preservability (weathering resistance, water resistance) and provide an image with a high quality.

TECHNICAL FIELD

This invention relates to an ink for ink jet recording which gives arecorded image having a high quality, exhibits an excellent ejectionstability and provides an image with an excellent preservability, aprocess for the production of said ink and an ink jet recording processusing said ink.

BACKGROUND ART

In recent years, with the spread of computers, ink jet printers havebeen widely used to print on paper, film, cloth, etc. at offices as wellas at home.

Examples of ink jet recording method include a method which allows apiezoelectric element to give pressure that causes a droplet to beejected, a method which comprises heating the ink to generate bubbles,causing a droplet to be ejected, a method involving the use ofultrasonic wave, and a method which uses electrostatic force to suck anddischarge a droplet. As inks for these ink jet recording methods thereare used aqueous inks, oil-based inks and solid (melt type) inks. Amongthese inks, aqueous inks are mainly used from the standpoint ofproducibility, handleability, odor, safety, etc.

The dyes to be incorporated in these inks for ink jet recording arerequired to exhibit a high solubility in solvents, allow a high densityrecording and have a good hue and an excellent fastness to light, heat,air, water and chemical, a good fixability to image-receiving materials,difficulty in running, an excellent preservability, no toxicity and ahigh purity and be available at a low cost.

However, it is extremely difficult to seek dyes meeting theserequirements to a high extent. In particular, dyes having a good cyanhue and an excellent weathering resistance have been keenly desired.

Various dyes and pigments have been already proposed for ink jetrecording and have been actually used. However, no dyes meeting allthese requirements have been found yet. Known dyes and pigments providedwith color index (C.I.) can difficultly satisfy both the hue andfastness requirements for inks for ink jet recording. As dyes whichenhance fastness there have been proposed azo dyes derived from aromaticamines and 5-membered heterocyclic amines in JP-A-55-161856. However,these dyes are disadvantageous in that they assume an undesirable hue inthe yellow and cyan ranges and thus cause deterioration of colorreproducibility. Inks for ink jet recording which are intended tosatisfy requirements for both hue and light-fastness are disclosed inJP-A-61-36362 and JP-A-2-212566. However, the dyes used in thesepatents, if used as water-soluble inks, leave something to be desired insolubility in water. Further, when the dyes described in these patentsare used as water-soluble inks for ink jet, problems arise with moistheat fastness as well. As a means for solving these problems there hasbeen proposed the use of the compound and ink described inJP-T-11-504958 (the term “JP-T” as used herein means a publishedJapanese translation of a PCT patent application). Further, referencehas been made to inks for ink jet recording comprising pyrazolylanilineazo for improving hue or light-fastness (Japanese Patent Application No.2000-80733). However, these inks for ink jet recording leave somethingto be desired in both color reproducibility and fastness of outputtedimage.

It has been further made obvious that images recorded on an ink jetphotographic grade gloss paper sometimes show a remarkably poorpreservability when posted indoor. The inventors presume that thisphenomenon is attributed to some oxidizing gas in the air such as ozone.This phenomenon no longer occurs when the flow of air is blocked by somemeasure such as putting in glass-fronted frame.

This phenomenon occurs remarkably with ink jet photographic grade glosspaper and thus brings forth a great problem with the related art ink jetrecording process featuring photographic grade as one of its importantadvantages.

Therefore, an aim of the present invention is to provide an ink for inkjet recording comprising an aqueous ink which allows ejection with ahigh stability and gives an image having a good hue, an excellentlight-fastness and water resistance, no defects in image quality such asrunning of fine line and a good preservability under severe conditionsfrom the standpoint of handleability, odor, safety, etc. Another aim ofthe present invention is to provide an ink set which allows ejection ofeven an ink aged over an extended period of time or under severeconditions with a high stability.

Disclosure of the Present Invention

The characteristic of the ink for ink jet recording of this invention isthat an ink for ink jet recording having the following phthalocyaninedye dissolved or dispersed in an aqueous medium has at least one of thefollowing properties. Preferred is an ink that satisfies all thefollowing requirements (1) to (4).

-   (1) The viscosity of the aforementioned ink at 25° C. is from 1 to    50 mPa·sec, preferably from 1 to 20 mPa·sec.-   (2) The conductivity of the aforementioned ink is from not smaller    than 0.01 S/m to not greater than 10 S/m.-   (3) The static surface tension of the aforementioned ink at 25° C.    is from 25 to 50 mN/m.-   (4) The percent change of viscosity and surface tension of the    aforementioned ink from at 25° C. to at 10° C. is not greater than    250% and not greater than 130%, respectively.

The characteristic of the process for the production of an ink for inkjet recording of this invention is that the process for the productionof an ink for ink jet recording comprises at least a step of applyingultrasonic vibration and/or in the process for the production of an inkfor ink jet recording, the ink for ink jet recording thus prepared isfiltered through a filter having pores of an effective diameter of notgreater than 1 μm and defoamed before use.

The aforementioned aims of this invention were solved by the followingdesirable means.

1. An ink for ink jet recording, comprising a aqueous medium and aphthalocyanine dye dissolved or dispersed in the aqueous medium, whereinthe phthalocyanine dye is a water-soluble dye having an oxidationpotential of more positive than 1.0 and the ink has a conductivity of0.01 S/m to 10 S/m.

2. The ink for ink jet recording according to claim 1, which has aviscosity of 1 to 20 mPa·sec at 25° C.

3. The ink for ink jet recording according to claim 1 or 2, which has astatic surface tension of 25 to 50 mN/m at 25° C.

4. The ink for ink jet recording according to claim 2 or 3, wherein aviscosity of the ink has a viscosity ratio of not greater than 250% fromat 25° C. to at 10° C., and a static surface tension has a staticsurface tension ratio of not greater than 130% from at 25° C. to at 10°C.

5. The ink for ink jet recording according to any one of claims 1 to 4,which has a pH value of 4 to 12 at 25° C.

6. The ink for ink jet recording according to any one of claims 1 to 5,which has a dye remaining ratio (density after fading/initialdensity×100) of not smaller than 60%(preferably 80%) after 24 hours ofstorage in an atmosphere of 5 ppm ozone in a monochromatic area that isobtained by printing with a monochromatic ink (cyan) in such a manner acyan reflection density through a status A filer is from 0.9 to 1.1. 7.The ink for ink jet recording according to any one of claims 1 to 6,wherein the ink has Cu ions that are eluted with water in an amount ofnot greater than 20% of a total amount of the dye after an ozone fadingunder the conditions defined in 6.

8. The ink for ink jet recording according to any one of claims 1 to 7,wherein the phthalocyanine dye is the water-soluble dye having anelectron-withdrawing group at β-position of a benzene ring in thephthalocyanine.

9. The ink for ink jet recording according to any one of claims 1 to 8,wherein the phthalocyanine dye is the water-soluble dye that is producedby a process which doesn't pass through a sulfonati ozone fading on ofan unsubstituted phthalocyanine.

10. The ink for ink jet recording according to any one of claims 1 to 9,wherein the phthalocyanine dye is represented by the following formula(I):

wherein X₁, X₂, X₃ and X₄ each independently represent —SO-Z, —SO₂-Z,—SO₂NR₁R₂, sulfo group, —CONR₁R₂ or —CO₂R₁; Z represents a substitutedor unsubstituted alkyl group, substituted or unsubstituted cycloalkylgroup, substituted or unsubstituted alkenyl group, substituted orunsubstituted aralkyl group, substituted or unsubstituted aryl group orsubstituted or unsubstituted heterocyclic group; R₁ and R₂ eachindependently represent a hydrogen atom, substituted or unsubstitutedalkyl group, substituted or unsubstituted cycloalkyl group, substitutedor unsubstituted alkenyl group, substituted or unsubstituted aralkylgroup, substituted or unsubstituted aryl group or substituted orunsubstituted heterocyclic group; and when there are a plurality of Z's,they may be the same or different;

-   Y₁, Y₂, Y₃ and Y₄ each independently represent a monovalent    substituent; and when there are a plurality of any of X₁ to X₄ and    Y₁ to Y₄, they may be the same or different; a₁ to a₄ and b₁ to b₄    represent the number of substituents X₁ to X₄ and Y_(1 to Y) ₄,    respectively; a₁ to a₄ each independently represent an integer of    from 0 to 4 and are not 0 at the same time; and b₁ to b₄ each    independently represent an integer of 0 to 4; and-   M represents a hydrogen atom, metal atom or oxide, hydroxide or    halide thereof.

11. The ink for ink jet recording according to claim 10, wherein the dyerepresented by the formula (I) is a dye represented by the followingformula (II):

wherein X₁₁ to X₁₄, Y₁₁ to Y₁₈ and M₁ each have the same meaning asthose in the formula (I); and a₁₁ to a₁₄ each independently represent aninteger of 1 or 2.

12. A method for ink jet recording, comprising using the ink for ink jetrecording according to claims 1 to 11.

13. A method for recording an image on an image-receiving material,comprising ejecting an ink droplet onto the image-receiving materialincluding an image-receiving layer containing an inorganic whiteparticulate pigment on a support according to a record signal,

-   -   wherein the ink droplet comprises the ink for ink jet recording        described in claims 1 to 11.

14. A method for producing the ink for ink jet recording according toclaims 1 to 11, which comprises at least applying a ultrasonicvibration.

15. A method for producing the ink for ink jet recording according toclaims 1 to 11,

-   -   wherein the ink for ink jet recording prepared is filtered        through a filter having pores of an effective diameter of not        greater than 1 μm and defoamed before use.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the temperature dependence of viscosityof light cyan ink and cyan ink of ink set 101 of Example 5.

FIG. 2 is a diagram illustrating the temperature dependence of surfacetension of light cyan ink and cyan ink of ink set 101 of Example 5.

BEST MODE FOR CARRYING OUT THE PRESENT INVENTION

The present invention will be further described hereinafter.

The present applicant made extensive studies of ink for ink jetrecording and, as a result, found that the requirements for the dyeare 1) good hue and no hue change (solvate), 2) excellent 1 resistance(light, ozone, NOx, solvent, oil, water), 3) safety (Ames, nocarcinogenecity, no skin stimulation, good decomosability), 4) low cost,5) high ε, 6) high solubility, and 7) high fixability to media.

Next, the requirements for ink physical properties and concentrated inkphysical properties are 1) uniform regardless of temperature and elapsedtime, 2) little stainability, 3) good penetration in media, 4) uniformsize of droplet, 5) applicability to any kind of paper, 6) easypreparation, 7) no misejection, low foamability and quick disappearanceof foam, and 8) stable ejection.

The requirements for image are 1) no running, discoloration and highcleaness without peeding, 2) scratch resistance, 3) high gloss anduniformity, 4) good image preservability and excellent discolorationbalance, 5) good dryability, 6) high speed of printing, and 7) no imagedensity dependence of percent discoloration. The physical propertiesrequired for ink for ink jet recording are that the ink is excellentboth in light-resistance and ozone resistance and shows a small changeof hue and surface conditions (difficulty in the occurrence of bronzeand the separation of dyes). Referring to light-resistance (OD1.0), itis desired that the ink show a light-resistance of not smaller than 90%as calculated in terms of dye remaining ratio (density afterdiscoloration/initial density×100) in 3 days when exposed to light froma Xenon lamp at 1.1 W/m (intermittent) through a TAC filter on a PMphotographic image-receiving paper produced by EPSON CO., LTD. It isalso desired that the ink show a dye remaining ratio of not smaller than85% in 14 days. Referring to ozone resistance, it is desired that theink show an ozone resistance of not smaller than 60% as calculated interms of dye remaining ratio in 1 day in an ozone atmosphere of notgreater than 5 ppm. It is further desired that the ink show an ozoneresistance of not smaller than 70%, particularly not smaller than 80%,as calculated in terms of dye remaining ratio in 1 day. It is alsodesired that the ink show an ozone resistance of not smaller than 25%,preferably not smaller than 40%, particularly not smaller than 50%, ascalculated in terms of dye remaining ratio in 5 days. Samples havingdifferent spreads of dye were prepared by GTC, and these samples wereeach measured for Cu content in dye by fluorescent X-ray.

When the phthalocyanine dye decomposes, Cu ion occurs in the form ofphthalate. It is desired that the amount of phthalate existing in theactual print as calculated in terms of Cu ion be not greater than 10mg/m². For the determination of the amount of Cu eluted from the print,a cyan solid image having a phthalate content of not greater than 20mg/m² as calculated in terms of Cu ion was formed. This image wasozone-faded, and the amount of ions eluted with water was then analyzed.Before fading, all the Cu compounds are trapped by the image-receivingmaterial. It is desired that the amount of ions eluted with water be notgreater than 20% based on the total amount of the dyes.

It was found in the present invention that a phthalocyanine dye havingthe aforementioned physical properties is accomplished by 1) faising theoxidation potential, 2) raising the associatability, 3) introducingassociation-acclerating groups and strengthening the hydrogen bondduring π-π stacking, 4) preventing substituents from being substitutedin α-position, that is, facilitating stacking, and effecting othermeasures.

The characteristic of the dye to be used in the ink for ink jetrecording of the present invention is that a phthalocyanine dye having aspecifiable number and position of substituents is used while thephthalocyanine dye used in the related art ink jet recording ink is onederived from an unsubstituted phthalocyanine by sulfonation and thus isa mixture having an unspecifiable number and position of substituents. Afirst structural characteristic is that the phthalocyanine dye of thepresent invention is a water-soluble phthalocyanine dye which is notderived via sulfonation of unsubstituted phthalocyanine. A secondstructural characteristic is that the phthalocyanine has anelectron-withdrawing group on some, preferably all of its benzene ringsin its α-position. In some detail, those substituted by a sulfonyl group(Japanese Patent Application No. 2001-47013, Japanese Patent ApplicationNo. 2001-190214), those substituted generally by a sulfamoyl group(Japanese Patent Application No. 2001-24352, Japanese Patent ApplicationNo. 2001-189982), those substituted by a heterocyclic sulfamoyl group(Japanese Patent Application No. 2001-96610, Japanese Patent ApplicationNo. 2001-190216), those substituted by a heterocyclic sulfonyl group(Japanese Patent Application No. 2001-76689, Japanese Patent ApplicationNo. 2001-190215), those substituted by a specific sulfamoyl group(Japanese Patent Application No. 2001-57063), those substituted by acarbonyl group (Japanese Patent Application No. 2002-012869), and thosehaving a specific substituent for enhancing solubility and ink stabilityand preventing bronze are preferred. Specific useful examples of thesecompounds include those having asymmetric carbon atoms (Japanese PatentApplication No. 2002-012868) and those in the form of lithium salt(Japanese Patent Application No. 2002-012864).

A first physical characteristic of the dye to be used in the ink for inkjet recording of the present invention is that it has a positiveoxidation potential. The oxidation potential is preferably more positivethan 1.00 V, more preferably more positive than 1.1 V, most preferablymore positive than 1.2 V. A second physical characteristic of the dye isthat it has a high associatability. Specific examples of such a dyeinclude oil-soluble dyes having a defined associatability (JapanesePatent Application No. 2001-64413) and water-soluble dyes having adefined associatability (Japanese Patent Application No. 2001-117350).

Referring to the relationship between the number of associating groupand the properties (absorbance of ink), the incorporation of associatinggroups causes easy occurrence of deterioration of absorbance or shift ofλmax to shorter wavelength even in a dilute solution. Referring to thenumber of associating groups and the properties (reflectance OD on PM920image-receiving paper produced by EPSON CO., LTD.), the more the numberof associating groups is, the lower is reflectance OD at the same ionintensity. In other words, association proceeds on the image-receivingpaper. Referring to the relationship between the number of associatinggroups and the properties (ozone resistance, light-resistance), the morethe number of associating groups is, the better is ozone resistance. Adye having a large number of associating groups tends to have animprovement in light-resistance as well. In order to provide ozoneresistance, it is necessary that the aforementioned substituent X (whichrepresents X₁ to X₄) be provided. Since there is a trade-offrelationship between reflectance OD and fastness, it is necessary thatlight-resistance be raised without deteriorating association.

Preferred examples of the ink of the present invention include:

-   1) cyan ink having a light-resistance of not smaller than 90% as    calculated in terms of dye remaining ratio in 3 days when exposed to    light from a xenon lamp at 1.1 W/m (intermittent) through a TAC    filter on a PM photographic image-receiving paper produced by EPSON    CO., LTD.;-   2) cyan ink having a dye remaining ratio (density after    discoloration/initial density×100) of not lower than 60% (preferably    80%) after 24 hours of storage in a 5 ppm ozone atmosphere on a    monochromatic area on which printing has been made with said    monochromatic ink (cyan) such that the cyan reflection density    through a status A filter reaches a range of from 0.9 to 1.1;-   3) cyan ink which has Cu ions eluted with water in an amount of not    greater than 20% based on the total amount of dyes after ozone    fading under the conditions 2; and-   4) cyan ink which can penetrate a specific image-receiving paper to    a depth of not smaller than 30% of the upper part of the    image-receiving layer.

The dye to be incorporated in the ink for ink jet recording of thepresent invention is a phthalocyanine dye which is preferably awater-soluble dye having an oxidation potential of more positive than1.0. More preferably, the water-soluble dye satisfies the aforementionedrequirements for fastness to ozone gas. Even more desirable among thesedyes is the phthalocyanine dye represented by the aforementioned formula(I).

A phthalocyanine dye has been known as a fast dye but has been known tohave a deteriorated fastness to ozone gas when used as a recording dyefor ink jet.

In the present invention, it is desired that an electron-withdrawinggroup be incorporated in the phthalocyanine skeleton to keep itsoxidation potential more positive than 1.0 V (vs SCE) in order to lowerthe reactivity with ozone, which is an electrophilic agent. It isdesired that the oxidation potential be as high as possible. Theoxidation potential is more preferably more positive than 1.1 V (vsSCE), most preferably more positive than 1.2 V (vs SCE).

The value of oxidation potential (Eox) can be easily measured by thoseskilled in the art. For the details of this method, reference can bemade to P. Delahay, “New Instrumental Methods in Electrochemistry”,interscience Publishers, 1954, A. J. Bards et al, “ElectrochemicalMethods”, John Wiley & Sons, 1980, Akira Fujishima et al, “Denki KagakuSokuteiho (Method for Electrochemical Measurement)”, Gihodo Shuppansha,1984, etc.

In some detail, for the measurement of oxidation potential, the testspecimen is dissolved in a solvent such as dimethyl formamide andacetonitrile containing a supporting electrolyte such as sodiumperchlorate and tetrapropylammonium perchlorate in a concentration offrom 1×10⁻⁴ to 1×10⁻⁶ mol/l. The solution is then measured for oxidationpotential with respect to SCE (saturated calomel electrode) by cyclicvoltametry or DC polarography. This value may deviate by a score ofmillivolts when affected by the difference in potential between liquidsor the resistivity of sample solution, but the reproducibility ofpotential can be assured by putting a standard sample (e.g.,hydroquinone) in the sample solution.

In order to unequivocally define oxidation potential, in the presentinvention, the value (vs SCE) measured by DC polarography in dimethylformamide containing 0.1 mol dm⁻³ of tetrapropylammonium perchlorate asa supporting electrolyte (dye concentration: 0.001 mol dm⁻³) is definedas oxidation potential of dye.

The value of Eox (oxidation potential) represents the transferability ofelectron from the sample to the electrode. the greater the value of Eoxis (the more positive the oxidation potential is), the more difficultlycan be transferred electron from the sample to the electrode, that is,the more difficultly can be oxidized the sample. Referring to therelation with the structure of the compound, the oxidation potential ismade more positive by incorporating an electron-withdrawing group andlower by incorporating an electron-donating group. In the presentinvention, in order to reduce the reactivity with ozone, which is anelectrophilic agent, it is desired that the oxidation potential be mademore positive by incorporating an electron-withdrawing group in thephthalocyanine skeleton. Accordingly, it can be said that when Hammett'ssubstituent constant σp value, which is an electron-withdrawing orelectron-donative measure of substituent, is used, the oxidationpotential can be made more positive by incorporating a substituenthaving a great σp value such as sulfinyl group, sulfonyl group andsulfamoyl group.

For the reason of adjustment of potential as well, a phthalocyanine dyerepresented by the aforementioned formula (I) is preferably used.

The fact that the phthalocyanine dye having the aforementioned oxidationpotential is a cyan dye excellent both in light-resistance and ozoneresistance is made obvious from the fact that the phthalocyanine dyesatisfies the aforementioned requirements for light-resistance and ozoneresistance.

The phthalocyanine dye to be used in the present invention (preferablyphthalocyanine dye represented by the formula (I)) will be furtherdescribed hereinafter.

In the formula (I), X₁, X₂, X₃ and X₄ each independently represent—SO-Z, —SO₂-Z, —SO₂NR₁R₂, sulfo group, —CONR₁R₂ or —CO₂R₁. Preferredamong these substituents are —SO-Z, —SO₂-Z, —SO₂NR₁R₂ and —CONR₁R₂,particularly —SO₂-Z and —SO₂NR₁R₂, most preferably —SO₂-Z. When any ofa1 to a4, which each indicate the number of substituents, represents anumber not smaller than 2, those which are present in a plurality amongX₁ to X₄ may be the same or different and each independently representany of the aforementioned groups. X₁, X₂, X₃ and X₄ may be the samesubstituent or may be altogether a substituent of the same kind buthaving different moieties, e.g., —SO₂-Z in which Z differs among X₁ toX₄ or each may contain different substituents, e.g., —S O₂— Z and—SO₂NR₁R₂.

The aforementioned Z groups each independently represent a substitutedor unsubstituted alkyl group, substituted or unsubstituted cycloalkylgroup, substituted or unsubstituted alkenyl group, substituted orunsubstituted aralkyl group, substituted or unsubstituted aryl group orsubstituted or unsubstituted heterocyclic group. Preferred among thesegroups are substituted or unsubstituted alkyl group, substituted orunsubstituted aryl group or substituted or unsubstituted heterocyclicgroup, most preferably substituted alkyl group, substituted aryl groupand substituted heterocyclic group.

The aforementioned R₁ and R₂ groups each independently represent ahydrogen atom, substituted or unsubstituted alkyl group, substituted orunsubstituted cycloalkyl group, substituted or unsubstituted alkenylgroup, substituted or unsubstituted aralkyl group, substituted orunsubstituted aryl group or substituted or unsubstituted heterocyclicgroup. Preferred among these groups are hydrogen atom, substituted orunsubstituted alkyl group, substituted or unsubstituted aryl group orsubstituted or unsubstituted heterocyclic group, more preferablyhydrogen atom, substituted alkyl group, substituted aryl group orsubstituted heterocyclic group. However, it is not desired that both R₁and R₂ be a hydrogen atom.

The substituted or unsubstituted alkyl group represented by R₁, R₂ and Zis preferably an alkyl group having from 1 to 30 carbon atoms. Inparticular, for the reason of enhancement of solubility of dye orstability of ink, the alkyl group is preferably branched, and an alkylgroup having asymmetric carbon atoms (used in the form of racemate) isparticularly preferred. Examples of the substituents include the samesubstituents as used in the case where Z, R₁, R₂, Y₁, Y₂, Y₃ and Y₄ canfurther have substituents as described later. Particularly preferredamong these substituents are hydroxyl group, ether group, ester group,cyano group, amide group and sulfonamide group because they enhance theassociatability and hence the fastness of dye. Further, halogen atom orionic hydrophilic group may be included. The number of carbon atoms inthe alkyl group doesn't include that of carbon atoms in thesubstituents. This applies to the other groups.

The substituted or unsubstituted cycloalkyl group represented by R₁, R₂and Z is preferably a cycloalkyl group having from 5 to 30 carbon atoms.In particular, for the reason of enhancement of solubility of dye orstability of ink, a cycloalkyl group having asymmetric carbon atoms(used in the form of racemate) is particularly preferred. Examples ofthe substituents include the same substituents as used in the case whereZ, R₁, R₂, Y₁, Y₂, Y₃ and Y₄ can further have substituents as describedlater. Particularly preferred among these substituents are hydroxylgroup, ether group, ester group, cyano group, amide group andsulfonamide group because they enhance the associatability and hence thefastness of dye. Further, halogen atom or ionic hydrophilic group may beincluded.

The substituted or unsubstituted alkenyl group represented by R₁, R₂ andZ is preferably an alkenyl group having from 2 to 30 carbon atoms. Inparticular, for the reason of enhancement of solubility of dye orstability of ink, the alkenyl group is preferably branched, and analkenyl group having asymmetric carbon atoms (used in the form ofracemate) is particularly preferred. Examples of the substituentsinclude the same substituents as used in the case where Z, R₁, R₂, Y₁,Y₂, Y₃ and Y₄ can further have substituents as described later.Particularly preferred among these substituents are hydroxyl group,ether group, ester group, cyano group, amide group and sulfonamide groupbecause they enhance the associatability and hence the fastness of dye.Further, halogen atom or ionic hydrophilic group may be included.

The substituted or unsubstituted aralkyl group represented by R₁, R₂ andZ is preferably an aralkyl group having from 7 to 30 carbon atoms. Inparticular, for the reason of enhancement of solubility of dye orstability of ink, the aralkyl group is preferably branched, and anaralkyl group having asymmetric carbon atoms (used in the form ofracemate) is particularly preferred. Examples of the substituentsinclude the same substituents as used in the case where Z, R₁, R₂, Y₁,Y₂, Y₃ and Y₄ can further have substituents as described later.Particularly preferred among these substituents are hydroxyl group,ether group, ester group, cyano group, amide group and sulfonamide groupbecause they enhance the associatability and hence the fastness of dye.Further, halogen atom or ionic hydrophilic group may be included.

The substituted or unsubstituted aryl group represented by R₁, R₂ and Zis preferably an aralkyl group having from 6 to 30 carbon atoms.Examples of the substituents include the same substituents as used inthe case where Z, R₁, R₂, Y₁, Y₂, Y₃ and Y₄ can further havesubstituents as described later. Particularly preferred among thesesubstituents are electron-withdrawing groups because they make theoxidation potential of dye and thus enhance the fastness thereof.Examples of the electron-withdrawing groups include those the Hammett'ssubstituent constant op value of which is positive. Preferred amongthese substituents are halogen atom, heterocyclic group, cyano group,carboxyl group, acylamino group, sulfonamide group, sulfamoyl group,carbamoyl group, sulfonyl group, imide group, acyl group, sulfo group,and quaternary ammonium group, more preferably cyano group, carboxylgroup, sulfamoyl group, carbamoyl group, sulfonyl group, imide group,acyl group, sulfo group, and quaternary ammonium group.

The heterocyclic group represented by R₁, R₂ and Z is preferably a 5- or6-membered heterocyclic group which may be further condensed. Theheterocyclic group may also be an aromatic heterocyclic group ornonaromatic heterocyclic group. The heterocyclic group represented byR₁, R₂ and Z will be hereinafter exemplified in the form of heterocyclicring with the substitution position omitted but the substitutionposition is not limited. For example, pyridine can be substituted in 2-,3- and 4-positions. Examples of the heterocyclic group represented byR₁, R₂ and Z include pyridine, pyrazine, pyrimidine, pyridazine,triazine, quinoline, isoquinoline, quinazoline, cinnoline, phthaladine,quinoxaline, pyrrole, indole, furane, benzofurane, thiophene,benzothiophene, pyrazole, imidazole, benzimidazole, triazole, oxazole,benzoxazole, thiazole, benzothiazole, isothiazole, benzisothiazole,thiadiazole, isoxazole, benzisoxazole, pyrrolidine, piperidine,piperazine, imidazolidine, thiazoline, etc. Preferred among thesesubstituents are aromatic heterocyclic groups. Exemplifying thesearomatic heterocyclic groups as in the aforementioned case, pyridine,pyrazine, pyrimidine, pyridazine, triazine, pyrazole, imidazole,benzimidazole, triazole, thiazole, benzothiazole, isothiazole,benzisothiazole, and thiadiazole. These substituents may havesubstituents. Examples of the substituents include the same substituentsas used in the case where Z, R₁, R₂, Y₁, Y₂, Y₃ and Y₄ can further havesubstituents as described later. Preferred examples of thesesubstituents are the same as those in the aforementioned aryl group.Even more desirable examples of these substituents are the same as thosein the aforementioned aryl group.

Y₁ Y₂, Y₃ and Y₄ each independently represent a hydrogen atom, halogenatom, alkyl group, cycloalkyl group, alkenyl group, aralkyl group, arylgroup, heterocyclic group, cyano group, hydroxyl group, nitro group,amino group, alkylamino group, alkoxy group, aryloxy group, acylaminogroup, arylamino group, ureide group, sulfamoylamino group, alkylthiogroup, arylthio group, alkoxycarbonylamino group, sulfonamide group,carbamoyl group, sulfamoyl group, sulfonyl group, alkoxycarbonyl group,heterocyclic oxy group, azo group, acyloxy group, carbamoyloxy group,silyloxy group, aryloxycarbonyl group, aryloxycarbonylamino group, imidegroup, heterocyclic thio group, phosphoryl group, acyl group, carboxylgroup or sulfo group which may further have substituents.

Preferred among these groups are hydrogen atom, halogen atom, alkylgroup, aryl group, cyano group, alkoxy group, amide group, ureide group,sulfonamide group, carbamoyl group, sulfamoyl group, alkoxycarbonylgroup, carboxyl group, and sulfo group. Particularly preferred amongthese groups are hydrogen atom, halogen atom, cyano group, carboxylgroup, and sulfo group, most preferably hydrogen atom.

When Z, R₁, R₂, Y₁, Y₂, Y₃ and Y₄ each are a group which can furtherhave substituents, they may further have the following substituents.

Examples of these substituents include straight-chain or branched alkylgroup having from 1 to 12 carbon atoms, straight-chain or branchedaralkyl group having from 7 to 18 carbon atoms, straight-chain orbranched alkenyl group having from 2 to 12 carbon atoms, straight-chainor branched alkinyl group having from 2 to 12 carbon atoms,straight-chain or branched cycloalkyl group having from 3 to 12 carbonatoms, straight-chain or branched cycloalkyl group having from 3 to 12carbon atoms (These groups each preferably have branches, particularlyasymmetric carbon atoms, for the reason of enhancement of solubility ofdye and stability of ink. Specific examples of these groups: methyl,ethyl, propyl, isopropyl, sec-butyl, t-butyl, 2-ethylhexyl,2-methylsulfonylethyl, 3-phenoxypropyl, trifluoromethyl, cyclopentyl),halogen atom (e.g., chlorine atom, bromine atom), aryl group (e.g.,phenyl, 4-t-butylphenyl, 2,4-di-t-amylphenyl), heterocyclic group (e.g.,imidazolyl, pyrazolyl, triazolyl, 2-furyl, 2-chenyl, 2-pyrimidinyl,2-benzothiazolyl), cyano group, hydroxyl group, nitro group, carboxylgroup, amino group, alkyloxy group (e.g., methoxy, ethoxy,2-methoxyethoxy, 2-methanesulfonylethoxy), aryloxy group (e.g., phenoxy,2-methylphenoxy, 4-t-butylphenoxy, 3-nitrophenoxy,3-t-butyloxycarbamoylphenoxy, 3-methoxycarbamoyl), acylamio group (e.g.,acetamide, benzamide, 4-(3-t-butyl-4-hydroxyphenoxy) butanamide),alkylamino group (e.g., methylamino, butylamino, diethylamino,methylbutylamino), anilino group (e.g., phenylamino, 2-chloroanilino),ureide group (e.g., phenylureide, methylureide, N,N-dibutylureide),sulfamoylamino group (e.g., N,N-dipropylsulfamoylamino), alkylthio group(e.g., methylthio, octylthio, 2-phenoxyethylthio), arylthio group (e.g.,phenylthio, 2-butoxy-5-t-octylphenylthio, 2-carboxyphenylthio),alkyloxycarbonylamino group (e.g., methoxycarbonylamino), sulfonamidegroup (e.g., methanesulfonamide, benzenesulfonamide,p-toluenesulfonamide), carbamoyl group (e.g., N-ethylcarbamoyl,N,N-dipropylsulfamoyl, N-phenylsulfamoyl), sulfonyl group (e.g.,methanesulfonyl, octanesulfonyl, benzenesulfonyl, toluenesulfonyl),alkyloxycarbonyl group (e.g., methoxycarbonyl, butyloxycarbonyl),heterocyclic oxy group (e.g., 1-phenyltetrazole-5-oxy,2-tetrahydropyeranyloxy), azo group (e.g., phenylazo,4-methoxyphenylazo, 4-pivaloylaminophenylazo,2-hydroxy-4-propanylphenylazo), acyloxy group (e.g., acetoxy),carbamoyloxy group (e.g., N-methylcarbamoyloxy, N-phenylcarbamoyloxy),silyloxy group (e.g., trimethylsilyloxy, dibutylmethylsilyloxy),aryloxycarbonylamino group (e.g., phenoxycarbonylamino), imide group(e.g., N-succinimide, N-phthalimide), heterocyclic thio group (e.g.,2-benzothiazolylthio, 2,4-di-phenoxy-1,3,5-triazole-6-thio,2-pyridylthio), sulfinyl group (e.g., 3-phenoxypropylsulfinyl),phosphonyl group (e.g., phenoxyphosphonyl, octyloxyphosphonyl,phenylphosphonyl), aryloxycarbonyl group (e.g., phenoxycarbonyl), acylgroup (e.g., acetyl, 3-phenylpropanoyl, benzoyl), and ionicallyhydrophilic group (e.g., carboxyl group, sulfo group, phosphono groupand quaternary ammonium group).

The phthalocyanine dye represented by the aforementioned formula (I), ifit is water-soluble, preferably has an ionically hydrophilic group.Examples of the ionically hydrophilic group include sulfo group,carboxyl group, phosphono group, quaternary ammonium group, etc.Preferred among the aforementioned ionically hydrophilic groups arecarboxyl group, phosphono group, and sulfo group, particularly carboxylgroup and sulfo group. The carboxyl group, phosphono group and sulfogroup may be in the form of salt. Examples of the counter ion formingthe salt include ammonium ions, alkaline metal ions (e.g., lithium ion,sodium ion, potassium ion), and organic cations (e.g.,tetramethylammonium ion, tetramethylguanidium ion,tetramethylphosphonium). Preferred among these counter ions are alkalinemetal salts. In particular, lithium salts are preferred because theyenhance solubility of dye and stability of ink.

Referring to the number of ionically hydrophilic groups, it is desiredthat at least two ionically hydrophilic groups be contained per moleculeof phthalocyanine-based dye. It is particularly desired that at leasttwo sulfo groups and/or carboxyl groups be contained per molecule ofphthalocyanine-based dye.

The suffixes a1 to a4 and b1 to b4 represent the number of substituentsX₁ to X₄ and Y₁ to Y₄, respectively. The suffixes a1 to a4 eachindependently represent an integer of from 0 to 4 but are not 0 at thesame time. The suffixes b1 to b4 each independently represent an integerof from 0 to 4. When any of a1 to a4 and any of b1 to b4 are an integerof not smaller than 2, any of X1 to X4 and any of Y1 to Y4 are presentin plurality. They may be the same or different.

The suffixes a1 and b1 satisfy the equation a1+b1=4. In a particularlypreferred combination of a1 and b1, a1 represents 1 or 2 and b1represents 3 or 2. In the best combination, a1 represents 1 and b1represents 3.

The various combinations of a1 and b1, a1 and b1 and a1 and b1 have thesame relationship as combination of a1 and b1. This applies also topreferred combinations.

M represents a hydrogen atom, metal element or oxide, hydroxide orhalide thereof.

Preferred examples of M include metal elements such as Li, Na, K, Mg,Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt,Cu, Ag, Au, Zn, Cd, Hg, Al, Ga, In, Si, Ge, Sn, Pb, Sb and Bi besidehydrogen atom. Preferred examples of the oxide include VO, GeO, etc.Preferred examples of the hydroxide include Si(OH)₂, Cr(OH)₂, Sn(OH) 2,etc. Further, examples of the halide include AlCl, SiCl₂, VCl, VCl₂,VOCl, FeCl, GaCl, ZrCl, etc. Preferred among these metal elements areCu, Ni, Zn, Al, etc., most preferably Cu.

Further, Pc (phthalocyanine ring) may form a dimer (e.g., Pc-M-L-M-Pc)or a trimer via L (divalent connecting group) wherein M's may be thesame or different.

Preferred examples of the divalent connecting group represented by Linclude oxy group-O—, thio group-S—, carbonyl group-CO—, sulfonylgroup-SO₂—, imino group-NH—, methylene group-CH₂—, and groups formed bycombination thereof.

Referring to a preferred combination of substituents on the compoundrepresented by the formula (I), at least one of the various substituentsis preferably a compound which is a preferred group as mentioned above.More preferably, more of the various substituents are compounds whichare preferred groups as mentioned above. Most preferably, all thevarious substituents are compounds which are preferred groups asmentioned above.

Even more desired among the phthalocyanine dyes represented by theaforementioned formula (I) is the phthalocyanine dye having a structurerepresented by the aforementioned formula (II). The phthalocyanine dyerepresented by the aforementioned formula (II) of the present inventionwill be further described hereinafter.

In the aforementioned formula (II), X₁₁ to X₁₄ and Y₁₁ to Y₁₈ have thesame meaning as X₁ to X₄ and Y₁ to Y₄ in the formula (I), respectively.Preferred examples of X₁₁ to X₁₄ and Y₁₁ to Y₁₈ include those listedwith reference to the formula (I). M₁ has the same meaning as M in theformula (I). Preferred examples of M₁ include those listed withreference to the formula (I).

In the formula (II), a₁₁ to a₁₄ each independently represent an integerof 1 or 2. Preferably, the sum of a₁₁, a₁₂, a₁₃ and a₁₄ is from notsmaller than 4 to not greater than 6.

It is particularly preferred that a₁₁, a₁₂, a₁₃ and a₁₄ each are 1.

X₁₁, X₁₂, X₁₃ and X₁₄ may be the same substituent. Alternatively, X₁₁,X₁₂, X₁₃ and X₁₄ each may be —SO₂-Z in which Z differs among X₁, X₂, X₃and X₄. Thus, X₁₁, X₁₂, X₁₃ and X₁₄ each may be a substituent of thesame kind but partially different. Alternatively, X₁₁, X₁₂, X₁₃ and X₁₄may be different substituents, e.g., —SO₂-Z, —SO₂NR₁R₂.

Particularly preferred examples of the combination of substituents amongthe phthalocyanine dyes represented by the formula (II) will be givenbelow.

Preferably, X₁₁ to X₁₄ each independently represent —SO-Z, —SO₂-Z,—SO₂NR₁R₂ or —CONR₁R₂, particularly —SO₂-Z or —SO₂NR₁R₂, most preferably—SO₂-Z.

Z each independently represents a substituted or unsubstituted alkylgroup, substituted or unsubstituted aryl group or substituted orunsubstituted heterocyclic group. Most desirable among these groups aresubstituted alkyl group, substituted aryl and substituted heterocyclicgroup. Particularly for the reason of enhancement of dye solubility orink stability, it is preferred that the substituents have asymmetriccarbons (used in racemate form). Further, for the reason of enhancementof association and hence fastness, it is preferred that the substituentshave a hydroxyl group, ether group, ester group, cyano group, amidegroup or sulfonamide group incorporated therein.

R₁ and R₂ each independently represent a hydrogen atom, substituted orunsubstituted alkyl group, substituted or unsubstituted aryl group orsubstituted or unsubstituted heterocyclic group, particularly a hydrogenatom, substituted alkyl group, substituted aryl group or substitutedheterocyclic group. However, it is not preferred that R₁ and R₂ each area hydrogen atom at the same time. Particularly for the reason ofenhancement of dye solubility or ink stability, it is preferred that thesubstituents have asymmetric carbons (used in racemate form). Further,for the reason of enhancement of association and hence fastness, it ispreferred that the substituents have a hydroxyl group, ether group,ester group, cyano group, amide group or sulfonamide group incorporatedtherein.

Y₁₁ to Y₁₈ each independently represent a hydrogen atom, halogen atom,alkyl group, aryl group, cyano group, alkoxy group, amide group, ureidegroup, sulfonamide group, carbamoyl group, sulfamoyl group,alkoxycarbonyl group, carboxyl group or sulfo group, particularlyhydrogen atom, halogen atom, cyano group, carboxyl group or sulfo group,most preferably hydrogen atom.

The suffixes a11 to a14 each independently represent 1 or 2. It isparticularly preferred that a11 to a14 each be 1 at the same time.

M₁ represents a hydrogen atom, metal element or oxide, hydroxide orhalide thereof, particularly Cu, Ni, Zn or Al, most preferably Cu.

The phthalocyanine dye represented by the formula (II), if it iswater-soluble, preferably has an ionically hydrophilic group. Examplesof the ionically hydrophilic group include sulfo group, carboxyl group,phosphono group, and quaternary ammonium group. Preferred among theseionically hydrophilic groups are carboxyl group, phosphono group, andsulfo group. Particularly preferred among these ionically hydrophilicgroups are carboxyl group and sulfo group. The carboxyl group, phosphonogroup and sulfo group may be used in the form of salt. Examples of thecounter ion forming the salt include ammonium ion, alkalinemetal ion(e.g., lithiumion, sodiumion, potassium ion), and organic cation (e.g.,tetramethylammonium ion, tetramethylguanidium ion,tetramethylphosphonium ion). Preferred among these counter ions arealkaline metal ions. Particularly preferred among these counter ions islithium ion because it enhances the dye solubility and hence the inkstability.

The number of ionically hydrophilic groups is preferably at least 2 permolecule of phthalocyanine-based dye. It is particularly preferred thatthere be contained at least two sulfo groups and/or carboxyl groups inthe phthalocyanine-based dye.

Referring to preferred combination of substituents on the compoundrepresented by the formula (II), the compound of the formula (II)preferably has various substituents at least one of which is one of thepreferred groups listed above. More preferably, more of the varioussubstituents are the preferred groups listed above. Most preferably, allof the various substituents are the preferred groups listed above.

Referring to the chemical structure of the phthalocyanine dye accordingto the present invention, it is preferred that at least oneelectron-withdrawing group such as sulfinyl group, sulfonyl group andsulfamoyl group be incorporated in each of four benzene rings in thephthalocyanine such that σp value of the substituents in the entirephthalocyanine skeleton totals not smaller than 1.6.

The Hammett's substituent constant σp as used herein will be somewhatdescribed hereinafter. Hammett's rule is an empirical rule which L. P.Hammett proposed in 1935 to quantitatively discuss the effect ofsubstituents on the reaction or equilibrium of benzene derivatives. Thevalidity of this empirical rule has been widely accepted today.Substituent constants required in Hammett's rule are σp value and σmvalue. These values are found in many general literatures. For thedetails of these values, reference can be made to J. A. Dean, “Lange'sHandbook of Chemistry”, 12th ed., 1979 (Mc Graw-Hill), and “Kagaku noRyoiki (Region of Chemistry)”, extra edition, No. 122, pp. 96-103, 1979(Nankodo).

The phthalocyanine derivative represented by the formula (I) is normallya mixture of analogues which are unavoidably different in introductionsites of substituents Xn (n=1 to 4) and Ym (m=1 to 4) and introducednumber of these substituents by synthesis method. Accordingly, theformula of the phthalocyanine dye is mostly a statistically averagedrepresentation of these analogous mixtures. In the present invention, itwas found that the classification of these analogous mixtures into thefollowing three classes gives a specific mixture which is particularlypreferred. In other words, mixtures of phthalocyanine-based dyeanalogues represented by the formulae (I) and (II) are classified intothe following classes for definition. In some detail, mixture ofphthalocyanine-based dye analogues represented by the aforementionedformulae (I) and (II) will be defined in the following threeclassifications. In the formula (II), Y₁₁, Y₁₂, Y₁₃, Y₁₄, Y₁₅, Y₁₆, Y₁₇,and Y₁₈ are in 1-position, 4-position, 5-position, 8-position,9-position, 12-position, 13-position and 16-position, respectively.

(1) β-position substitution type: Phthalocyanine dye having a specificsubstituent on 2- and/or 3-position, 6- and/or 7-position, 10- and/or11-position, or 14- and/or 15-position (2) α-position substitution type:Phthalocyanine dye having a specific substituent on 1- and/or4-position, 5- and/or 8-position, 9- and/or 12-position, or 13- and/or16-position (3) α,β-position mixed substitution type: Phthalocyanine dyehaving a specific substituent irregularly on 1- to 16-position.

In the specification, in order to describe phthalocyanine dyederivatives having different structures (particularly differentsubstitution positions), the aforementioned β-position substitutiontype, α-position substitution type and α,β-position mixed substitutiontype are used.

The phthalocyanine derivative to be used in the present invention can besynthesized by, e.g., methods described or cited in Shirai andKobayashi, “Phthalocyanine—Chemistry and Function—”, IPC Co., Ltd., pp.1 to 62, C. C. Leznoff-A.B.P. Lever, “Phthalocyanines—Properties andApplications”, VCH, pp. 1-54, etc. or analogous methods in combination.

The phthalocyanine compound represented by the formula (I) to be used inthe present invention can be synthesized by, e.g., sulfonation reaction,sulfonylchloration reaction and amidation reaction of unsubstitutedphthalocyanine compound as disclosed in World Patents 00/17275,00/08103, 00/08101 and 98/41853 and JP-A-10-36471. In this case, sincesulfonation can occur on any position of the phthalocyanine nucleus, itis difficult to control the sulfonated number of substituents.Accordingly, when sulfo groups are incorporated under such a reactioncondition, the position and number of sulfo groups incorporated in thereaction product cannot be predetermined, unavoidably giving a mixtureof products having different numbers of substituents or substitutionpositions. Thus, since when this mixture is used as a starting materialto synthesize the compound of the present invention, a α,β-mixedsubstitution type mixture comprising some compounds having differentnumbers of substituents or substitution positions is obtained as acompound of the present invention because the number of heterocyclicgroup-substituted sulfamoyl groups or the substitution position cannotbe predetermined.

As previously mentioned, when many electron-withdrawing groups such assulfamoyl group are incorporated in the phthalocyanine nucleus, thephthalocyanine dye is provided with a more positive oxidation potentialand hence an enhanced ozone fastness. When synthesized according to theaforementioned method, it is unavoidable that the reaction mixturecontains a phthalocyanine dye having a small number ofelectron-withdrawing groups incorporated therein, i.e., lower oxidationpotential. Accordingly, in order to enhance the ozone fastness of thephthalocyanine dye, a synthesis method capable of inhibiting theproduction of a compound having a lower oxidation potential ispreferably employed.

The phthalocyanine compound represented by the formula (II) can bederived from a tetrasulfophthalocyanine compound obtained by, e.g.,reacting a phthalonitrile derivative (compound P) represented by thefollowing formula and/or a diiminoisoindoline derivative (compound Q)represented by the following formula with a metal compound representedby the formula (III) or reacting a 4-sulfophthalocyanine derivative(compound R) represented by the following formula with a metal compoundrepresented by the formula (III).

In these formulae, Xp corresponds to X₁₁, X₁₂, X₁₃ or X₁₄ in the formula(II). Yq and Yq′ each correspond to Y₁₁, Y₁₂, Y₁₃, Y₁₄, Y₁₅, Y₁₆, Y₁₇ orY₁₈ in the formula (II). In the compound R, M′ represents a cation.

Examples of the cation represented by M′ include alkaline metal ionssuch as Li, Na and K ions and organic cations such as triethylammoniumion and pyridinium ion.M−(Y)d  (III)wherein M is as defined in the formulae (I-b) and (II); Y represents amonovalent or divalent ligand such as halogen atom, acetate anion,acetyl acetonate and oxygen; and d represents an integer of from 1 to 4.

In other words, when synthesized according to the aforementioned method,desired substituents can be incorporated by a predetermined number. Inparticular, in order to introduce many electron-withdrawing groups tomake the oxidation potential more positive as in the present invention,the aforementioned synthesis method can be used because it is extremelyexcellent as compared with the aforementioned method for synthesis ofthe phthalocyanine compound of the formula (I).

The phthalocyanine compound represented by the formula (II) thusobtained is a mixture of compounds represented by the following formulae(a)-1 to (a)-4 which are isomeric with the substitution position on Xp,i.e., β-position substitution type mixture.

In the foregoing synthesis method, when the same compound is used as Xp,a β-position substitution type phthalocyanine dye wherein X₁₁, X₁₂, X₁₃and X₁₄ are the same substituent can be obtained. On the contrary, whendifferent materials are used in combination as Xp, a dye havingsubstituents of the same kind but partially different or a dye havingdifferent substituents can be synthesized. Among the dyes of the formula(II), these dyes having different electron-withdrawing substituents areparticularly desirable because they can adjust the solubility andassociation of the dye, the age stability of the ink, etc.

In the present invention, it was found very important for theenhancement of fastness that any of these substitution types has anoxidation potential of more positive than 1.0 V (vs SCE). The degree ofthis effect could not be expected from the related art. Although itsmechanism is not known in detail, a tendency was given that β-positionsubstitution type is obviously better than α,β-position mixedsubstitution type in hue, light fastness, ozone fastness, etc.

Specific examples of the phthalocyanine dyes represented by the formulae(I) and (II) (exemplary compounds I-1 to I-12 and exemplary compounds101 to 190) will be given below, the phthalocyanine dye to be used inthe present invention is not limited thereto.

Exemplary Compound

Specific examples of various combinations of (X₁, X₂), (Y₁₁, Y₁₂), (Y₁₃,Y₁₄), (Y₁₅, Y₁₆), and (Y₁₇, Y₁₈) are each independently not in order.

Compound No M X1 X2 Y11, Y12 Y13, Y14 Y15, Y16 Y17, Y18 101 Cu—SO₂—NH—CH₂—CH₂—SO₃Li —H —H, —H —H, —H —H, —H —H, —H 102 Cu

—H —Cl, —H —Cl, —H —Cl, —H —Cl, —H 103 Cu

—H —H, —H —H, —H —H, —H —H, —H 104 Cu

—H —H, —H —H, —H —H, —H —H, —H 105 Ni

—H —Cl, —H —Cl, —H —Cl, H —Cl, —H 106 Cu—SO₂—NH—CH₂—CH₂—SO₂—NH—CH₂—COONa —CN —H, —H —H, —H —H, —H —H, —H 107 Cu

—H —H, —H —H, —H —H, —H —H, —H 108 Cu —SO₂—CH₂—CH₂—CH₂—SO₃Li —H —H, —H—H, —H —H, —H —H, —H 109 Cu —SO₂—CH₂—CH₂—CH₂—SO₃K —H —H, —H —H, —H —H,—H —H, —H 110 Cu —SO₂—(CH₂)₅—CO₂K —H —H, —H —H, —H —H, —H —H, —H 111 Cu

—H —H, —H —H, —H —H, —H —H, —H 112 Cu

—SO₃Li —H, —H —H, —H —H, —H —H, —H 113 Cu

—H —H, —H —H, —H —H, —H —H, —H 114 Cu

—SO₃Li —H, —H —H, —H —H, —H —H, —H 115 Cu

—H —H, —H —H, —H —H, —H —H, —H 116 Cu

—H —H, —H —H, —H —H, —H —H, —H 117 Cu

—H —H, —H —H, —H —H, —H —H, —H 118 Cu

—H —H, —H —H, —H —H, —H —H, —H 119 Cu

—H —H, —H —H, —H —H, —H —H, —H 120 Cu

—H —H, —H —H, —H —H, —H —H, —H 121 Cu

—H —H, —H —H, —H —H, —H —H, —H 122 Cu

—H —H, —H —H, —H —H, —H —H, —H 123 Cu —SO₂NH—C₈H₁₇(t) —H —H, —H —H, —H—H, —H —H, —H 124 Cu

—H —H, —H —H, —H —H, —H —H, —H 125 Cu

—H —H, —H —H, —H —H, —H —H, —H 126 Cu

—H —H, —H —H, —H —H, —H —H, —H 127 Cu

—H —H, —H —H, —H —H, —H —H, —H 128 Zn

—CN —H, —H —H, —H —H, —H —H, —H 129 Cu

—H —Cl, —H —Cl, —H —Cl, —H —Cl, —H 130 Cu

—H —H, —H —H, —H —H, —H —H, —H 131 Cu

—H —H, —H —H, —H —H, —H —H, —H 132 Cu

—H —H, —H —H, —H —H, —H —H, —H 133 Cu

—H —H, —H —H, —H —H, —H —H, —H 134 Cu

—H —H, —H —H, —H —H, —H —H, —H 135 Cu

—H —H, —H —H, —H —H, —H —H, —H 136 Cu

—H —H, —H —H, —H —H, —H —H, —H 137 Cu

—H —H, —H —H, —H —H, —H —H, —H 138 Cu

—H —H, —H —H, —H —H, —H —H, —H 139 Cu

—Cl —H, —H —H, —H —H, —H —H, —H 140 Cu

—H —H, —H —H, —H —H, —H —H, —H 141 Cu

—H —H, —H —H, —H —H, —H —H, —H 142 Cu

—H —H, —H —H, —H —H, —H —H, —H 143 Cu

—H —H, —H —H, —H —H, —H —H, —H 144 Cu

—H —H, —H —H, —H —H, —H —H, —H 145 Cu —SO₂CH₂CH₂OCH₂CH₂OCH₂CH₂SO₃Li —H—H, —H —H, —H —H, —H —H, —H M-Pc(XP₁)_(m)(Xp₂)_(n) In the table, theintroduction sites of the substituents (Xp1) and (Xp2) in the β-positionsubstituents are not in order. Compound No. M Xp₁ m Xp₂ n 146 Cu

3

1 147 Cu —SO₂—NH—CH₂—CH₂SO₃Li 3

1 148 Cu

3 —SO₂NH—CH₂—CH₂—CH₂—SO₂—NH—CH₂—CH₂—O—CH₂—CH₂—OH 1 149 Cu

2

2 150 Cu —SO₂—NH—CH₂—CH₂—SO₂—NH—CH₂CH₂—COONa 3

1 151 Cu

3 —SO₂NH—CH₂—CH₂—O—CH₂—CH₂—OH 1 152 Cu

2.5 —SO₂—CH₂—CH₂—O—CH₂—CH₂—OH 1.5 153 Cu

2

2 154 Cu —SO₂—CH₂—CH₂—CH₂—SO₃Li 3

1 155 Cu —SO₂—CH₂—CH₂—CH₂—COOK 2

2 156 Cu —SO₂—CH₂—CH₂—CH₂—SO₃Li 3

1 157 Cu —SO₂—CH₂—CH₂—O—CH₂—CH₂—SO₃Li 2

2 158 Cu

3

1 159 Cu —SO₂NHCH₂CH₂—SO₃Li 3

1 160 Cu —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—SO₃Na 3

1 161 Cu —SO₂CH₂CH₂CH₂SO₃Li 3

1 162 Cu —SO₂CH₂CH₂CH₂SO₃Li 2 —SO₂CH₂CH₂OCH₂CH₂OCH₂CH₂OH 2 163 Cu—SO₂CH₂CH₂CH₂SO₃K 3

1 164 Cu —SO₂CH₂CH₂CH₂SO₃Li 2 —SO₂CH₂CH₂CH₂SO₂N(CH₂CH₂OH)₂ 2 165 Cu—CO—NH—CH₂—CH₂—SO₃K 3 —CO—NH—CH₂—CH₂—O—CH₂—CH₂—OH 1 166 Cu—CO—NH—CH₂—CH₂—SO₂—NH—CH₂—CH₂—COONa 3

1 167 Cu

2.5

1.5 168 Cu

2

2 169 Cu —CO₂—CH₂—CH₂—CH₂—SO₃Li 3

1 170 Cu —CO₂—CH₂—CH₂—CH₂COOK 2

2 171 Cu —CO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—SO₃Na 3

1 172 Cu —SO₂CH₂CH₂OCH₂CH₂O—CH₂CH₂SO₃K 2

2 173 Cu

2

2 174 Cu

3

1 175 Cu —SO₂(CH₂)₃SO₂NH(CH₂)₃N(CH₂CH₂OH)₂ 2

2 176 Cu

3

1 177 Cu —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 2

1 178 Cu —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—OH 3

1 179 Cu

2

2 180 Cu

3 —SO₂NH—CH₂—CH₂—SO₂NH—CH₂—CH₂—O—CH₂—CH₂—OH 1 181 Cu

3

1 182 Cu

2.5

1.5 183 Cu

2 —SO₂—CH₂—CH₂CH₂—SO₂—NH—(CH₂)₃—CH₂—O—CH₂CH₂—OH 2 184 Cu

3 —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 1 185 Cu

3 —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 1 186 Cu

3 —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—OH 1 187 Cu

3

1 188 Cu

3 —CO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 1 189 Cu

3

1 190 Cu

3 —CO—NH—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 1

The structure of the phthalocyanine compound represented by M-Pc(Xp₁)m(Xp₂)n in Tables 8 to 11 is as follows.

-   -   (X_(p1)'s each independently represent X_(p1) or X_(p2).)

The phthalocyanine dye represented by the formula (I) can be synthesizedaccording to the patent cited above. The phthalocyanine dye representedby the formula (II) can be synthesized by the aforementioned method aswell as the method disclosed in JP-A-2001-226275, JP-A-2001-96610,JP-A-2001-47013 and JP-A-2001-193638. The starting material,intermediate dye and synthesis route are not limited to those accordingto these methods.

The ink for ink jet recording of the present invention comprises theaforementioned phthalocyanine dye incorporation therein preferably in anamount of from 0.2 to 20% by weight, more preferably from 0.5 to 15% byweight.

The ink for ink jet recording of the present invention can be preparedby dissolving and/or dispersing the phthalocyanine dye in an aqueousmedium. The term “aqueous medium” as used herein is meant to indicatewater or a mixture of water and a water-miscible organic solventoptionally comprising additives such as wetting agent (preferably asurface active agent as dissolving aid or dispersing aid), stabilizerand preservative incorporated therein.

Examples of the water-miscible organic solvent employable herein includealcohols (e.g., methanol, ethanol, propanol, isopropanol, butanol,isobutanol, sec-butanol, t-butanol, pentanol, hexanol, cyclohexanol,benzyl alcohol), polyvalent alcohols (e.g., ethylene glycol, diethyleneglycol, triethylene glycol, polyethylene glycol, propylene glycol,dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol,pentanediol, glycerin, hexanetriol, thiodiglycol), glycol derivatives(e.g., ethylene glycol monomethyl ether, ethylene glycol monoethylether, ethylene glycol monobutyl ether, diethylene glycol monomethylether, diethylene glycol monobutyl ether, propylene glycol monomethylether, propylene glycol monobutyl ether, dipropylene glycol monomethylether, triethylene glycol monomethyl ether, ethylene glycol diacetate,ethylene glycol monomethyl ether acetate, triethylene glycol monomethylether, triethylene glycolmonoethyl ether, ethylene glycol monophenylether), amines (e.g., ethanolamine, diethanolamine, triethanolamine,N-methyldiethanolamine, N-ethyldiethanolamine, morpholine,N-ethylmorpholine, ethylene diamine, diethylene triamine, triethylenetetramine, polyethyleneimine, tetramethylpropylenediamine), and otherpolar solvents (e.g., formamide, N,N-dimethylformamide,N,N-dimethylacetamide, dimethylsulfoxide, sulfolane, 2-pyrrolidone,N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-oxazolidone,1,3-dimethyl-2-imidazolidinone, acetonitrile, acetone). Two or more ofthe water-miscible organic solvents may be used in combination.

The aforementioned phthalocyanine dye, if it is oil-soluble, may beemulsion-dispersed in an aqueous medium in the form of solution in ahigh boiling organic solvent to prepare the ink of the presentinvention.

The boiling point of the high boiling organic solvent to be used in thepresent invention is not lower than 150° C., preferably not lower than170° C.

Examples of the high boiling organic solvent employable herein includephthalic acid esters (e.g., dibutyl phthalate, dioctyl phthalate,dicyclohexyl phthalate, di-2-ethylhexyl phthalate, decyl phthalate,bis(2,4-di-tert-amylphenyl)isophthalate,bis(1,1-diethylpropyl)phthalate), phosphoric or phosphonic acid esters(e.g., diphenyl phosphate, triphenyl phosphate, tricresyl phosphate,2-ethylhexyl diphenyl phosphate, dioctyl butyl phosphate, tricyclohexylphosphate, tri-2-ethylhexyl phosphate, tridodecyl phosphate,di-2-ethylhexyl phenyl phosphate), benzoic acid esters (e.g.,2-ethylhexyl benzoate, 2,4-dichlorobenzoate, dodecyl benzoate,2-ethylhexyl-p-hydroxybenzoate), amides (e.g., N,N-diethyldodecaneamide,N,N-diethyllaurylamide), alcohols or phenols (e.g., isostearyl alcohol,2,4-di-tert-amylphenol), aliphatic esters (e.g., dibutoxyethylsuccinate, di-2-ethylhexyl succinate, 2-hexyldecyl tetradecanoate,tributyl citrate, diethyl azelate, isostearyl lactate, trioctylcitrate), aniline derivatives (e.g.,N,N-dibutyl-2-butoxy-5-tert-octylaniline), chlorinated paraffins (e.g.,paraffins having a chlorine content of from 10% to 80%), trimesic acidesters (e.g., tributyl trimesate), dodecyl benzene, diisopropylenenaphthalene, phenols (e.g., 2,4-di-tert-amylphenol, 4-dodecyloxyphenol,4-dodecyloxycarbonylphenol, 4-(4-dodecyloxy phenylsulfonyl)phenol),carboxylic acids (e.g., 2-(2,4-di-tert-amylphenoxybutyric acid,2-ethoxyoctanedecanoic acid), and alkylphosphoric acids (e.g., di-2(ethylhexyl) phosphoric acid, dipheylphosphoric acid).

The high boiling organic solvent may be used in an amount of from 0.01to 3 times, preferably from 0.01 to 1.0 times that of the oil-solubledye by weight.

These high boiling organic solvents may be used singly or in admixtureof two or more thereof [e.g., tricresyl phosphate and dibutyl phthalate,trioctyl phosphate and di (2-ethylhexyl) sebacate, dibutyl phthalate andpoly(N-t-butylacrylamide)].

For examples of compounds other than the aforementioned high boilingorganic solvents to be used in the present invention and/or methods forthe synthesis of these high boiling organic solvents, reference can bemade to U.S. Pat. Nos. 2,322,027, 2,533,514, 2,772,163, 2,835,579,3,594,171, 3,676,137, 3,689,271, 3,700,454, 3,748,141, 3,764,336,3,765,897, 3,912,515, 3,936,303, 4,004,928, 4,080,209, 4,127,413,4,193,802, 4,207,393, 4,220,711, 4,239,851, 4,278,757, 4,353,979,4,363,873, 4,430,421, 4,430,422, 4,464,464, 4,483,918, 4,540,657,4,684,606, 4,728,599, 4,745,049, 4,935,321, 5,013,639, European Patents276,319A, 286,253A, 289,820A, 309,158A, 309,159A, 309,160A, 509,311A,510,576A, East German Patents 147,009, 157,147, 159, 573, 225,240A,British Patent 2,091,124A, JP-A-48-47335, JP-A-50-26530, JP-A-51-25133,JP-A-51-26036, JP-A-51-27921, JP-A-51-27922, JP-A-51-149028,JP-A-52-46816, JP-A-53-1520, JP-A-53-1521, JP-A-53-15127,JP-A-53-146622, JP-A-54-91325, JP-A-54-106228, JP-A-54-118246,JP-A-55-59464, JP-A-56-64333, JP-A-56-81836, JP-A-59-204041,JP-A-61-84641, JP-A-62-118345, JP-A-62-247364, JP-A-63-167357,JP-A-63-214744, JP-A-63-301941, JP-A-64-9452, JP-A-64-9454,JP-A-64-68745, JP-A-1-101543, JP-A-1-102454, JP-A-2-792, JP-A-2-4239,JP-A-2-43541, JP-A-4-29237, JP-A-4-30165, JP-A-4-232946, andJP-A-4-346338.

In the present invention, the oil-soluble dye and the high boilingorganic solvent are used in the form of emulsion dispersion in anaqueous medium. During emulsion dispersion, a low boiling organicsolvent may be used in some cases from the standpoint ofemulsifiability. As such a low boiling organic solvent there may be usedan organic solvent having a boiling point of from about 30° C. to 150°C. at atmospheric pressure. Preferred examples of the organic solventemployable herein include esters (e.g., ethyl acetate, butyl acetate,ethyl propionate, β-ethoxyethyl acetate, methyl cellosolve acetate),alcohols (e.g., isopropyl alcohol, n-butyl alcohol, secondary butylalcohol), ketones (e.g., methyl isobutyl ketone, methyl ethyl ketone,cyclohexanone), amides (e.g., dimethylformamide, N-methylpyrrolidone),and ethers (e.g., tetrahydrofurane, dioxane). However, the presentinvention is not limited to these organic solvents.

The emulsion dispersion is effected to disperse an oil phase having adye dissolved in a high boiling organic solvent optionally mixed with alow boiling organic solvent in an aqueous phase mainly composed of waterto make minute oil droplets of oil phase. During this procedure,additives such as surface active agent, wetting agent, dye stabilizer,emulsion stabilizer, preservative and antifungal agent described latermay be added to either or both of the aqueous phase and the oil phase asnecessary.

The emulsification is normally accomplished by adding the oil phase tothe aqueous phase. Alternatively, a so-called emulsification methodinvolving the dropwise addition of an aqueous phase to an oil phase ispreferably used.

The emulsion dispersion may be effected with various surface activeagents. Preferred examples of the surface active agents employableherein include anionic surface active agents such as aliphatic acidsalt, alkylsulfuric acid ester, alkylbenzenesulfonate,alkylnaphthalenesulfonate, dialkylsulfosuccinate, alkylphosphoric acidesters, naphthalenesulfonic acid-formalin condensate andpolyoxyethylenealkylsulfuric acid ester, and nonionic surface activeagents such as polyoxyethylenealkyl ether, polyoxyethylenealkylallylether, polyoxyethylenealiphatic acid ester, sorbitanaliphatic acidester, polyoxyethylenesorbitanaliphatic acid ester,polyoxyethylenealkylamine, glycerinaliphatic acid ester andoxyethyleneoxypropylene block copolymer. Alternatively, SURFYNOLS(produced by Air Products & Chemicals Inc.), which are acetylene-basedpolyoxyethylene oxide surface active agents, are preferably used aswell. Further, amine oxide-based amphoteric surface active agents suchas N,N-dimethyl-N-alkylamine oxide may be used. Those listed as surfaceactive agents in JP-A-59-157, 636, pp. 37-38, and Research DisclosureNo. 308119 (1989) may be used.

As the surface active agent to be used in emulsification there may beused the same kind of surface active agent as added to adjust theaforementioned liquid physical properties of the ink for ink jetrecording, though differing in purpose. As a result, the surface activeagent to be used for this purpose can perform a function of adjustingthe physical properties of the ink.

For the purpose of stabilizing the ink shortly after emulsification, theaforementioned surface active agents may be used in combination with awater-soluble polymer. As such a water-soluble polymer there may bepreferably used a polyvinyl alcohol, polyvinyl pyrrolidone, polyethyleneoxide, polyacrylic acid, polyacrylamide or copolymer thereof. Further,natural water-soluble polymers such as polysaccharides, casein andgelatin may be preferably used.

For the purpose of stabilizing the dye dispersion, polyvinyls obtainedby the polymerization of acrylic acid esters, methacrylic acid esters,vinyl esters, acrylamides, methacrylamides, olefins, styrenes,vinylethers or acrylonitriles, polyurethanes, polyesters, polyamides,polyureas, polycarbonates, etc., which are substantially insoluble in anaqueous medium, may be used. These polymers preferably have —SO₃ ⁻ or—COO⁻. In the case where these polymers substantially insoluble in anaqueous medium are used, they are preferably used in an amount of notgreater than 20% by weight, preferably not greater than 10% by weightbased on the amount of the high boiling organic solvent.

In the case where emulsion dispersion is effected to disperse theoil-soluble dye or high boiling organic solvent to make an aqueous ink,a particularly important factor is control over the particle size of theaqueous ink. In order to enhance the color purity or density during theformation of an image by ink ejection, it is essential to reduce theaverage particle size. The volume-average particle diameter of theaqueous ink is preferably not greater than 1 μm, more preferably from 5nm to 100 nm.

The measurement of the volume-average particle diameter and the particlesize distribution of the dispersed particles can be easily accomplishedby any known method such as static light scattering method, dynamiclight scattering method, centrifugal sedimentation method and method asdisclosed in “Jikken Kagaku Koza (Institute of Experimental Chemistru)”,4th ed., pp. 417-418.

For example, measurement can be easily carried out by diluting the inkwith distilled water such that the particle concentration in the inkreaches 0.1% to 1% by weight, and then subjecting the solution tomeasurement using a commercially available volume-average particlediameter measuring instrument (e.g., Microtrack UPA (produced by NIKKISOCO., LTD.). Further, dynamic light scattering method utilizing laserdoppler effect is particularly preferred because it is capable ofmeasuring even small particle size.

The term “volume-average particle diameter” as used herein is meant toindicate average particle diameter weighted with particle volume, whichis obtained by dividing the sum of the product of the diameter and thevolume of individual particles in the aggregate of particles by thetotal volume of the particles. For the details of volume-averageparticle diameter, reference can be made to Souichi Muroi, “KoubunshiRatekkusuno Kagaku (Chemistry of Polymer Letexes)”, Koubunshi Kankokai,page 119.

It was also made obvious that the presence of coarse particles has anextremely great effect on the printing properties. In other words,coarse particles clog the head nozzle. Even if coarse particles don't goso far as to clog the head nozzle, the ink cannot be ejected or can bedeviated when ejected, giving a serious effect on the printingproperties. In order to prevent this trouble, it is important to keepthe number of particles having a diameter of not smaller than 5 μm andnot smaller than 1 μm in the resulting ink to 10 or less and 1,000 orless, respectively.

The removal of these coarse particles can be accomplished by any knownmethod such as centrifugal separation method and precision filtrationmethod. The separation step may be effected shortly after emulsiondispersion or shortly before the filling of the emulsion dispersioncomprising various additives such as wetting agent and surface activeagent in the ink cartridge.

As an effective unit for reducing the average particle diameter ofparticles and eliminating coarse particles there may be used amechanical emulsifier.

As such an emulsifier there may be used any known device such as simplestirrer, impeller type agitator, in-line agitator, mill type agitator(e.g., colloid mill) and ultrasonic agitator. The use of a high pressurehomogenizer is particularly preferred.

For the details of the mechanism of high pressure homogenizer, referencecan be made to U.S. Pat. No. 4,533,254, JP-A-6-47264, etc. Examples ofcommercially available high-pressure homogenizers include Gaulinhomogenizer (produced by A. P. V GAULLN INC.), microfluidizer (producedby MICROFLUIDEX INC.) and altimizer (produced by SUGINO MACHINELIMITED).

In recent years, a high pressure homogenizer having a mechanism foratomizing a material in a ultrahigh-pressure jet stream as disclosed inU.S. Pat. No. 5,720,551 is particularly useful in the emulsiondispersion of the present invention. An example of the emulsifier usinga ultrahigh jet stream is De BEE2000 (produced by BEE INTERNATIONALLTD.).

The pressure at which emulsion is carried out by a high pressureemulsion disperser is not lower than 50 MPa, preferably not lower than60 MPa, more preferably not lower than 180 MPa.

For example, the combined use of two or more emulsifiers as in a methodinvolving the emulsification by an agitated emulsifier followed by thepassage through a high pressure homogenizer is particularly preferred.Alternatively, a method is preferably used which comprises effecting theemulsion of the material using such an emulsifier, adding additives suchas wetting agent and surface active agent, and then passing the inkcomposition again through the high pressure homogenizer before beingfilled in the cartridge.

In the case where the dye composition comprises a low boiling organicsolvent incorporated therein in addition to the high boiling organicsolvent, it is preferred to remove the low boiling organic solvent fromthe standpoint of emulsion stability and safety/hygiene. The removal ofthe low boiling solvent can be accomplished by any known method such asevaporation method, vacuum evaporation method and ultrafiltration methoddepending on the solvent to be removed. The step of removing the lowboiling organic solvent is preferably effected as rapidly as possibleshortly after emulsification.

The ink of the present invention is characterized in that theconductivity thereof is from not lower than 0.1 S/m to not higher than10 S/m. Preferred within this range of conductivity is from not lowerthan 0.5 S/m to not higher than 5 S/m. When the conductivity of the inkfalls within the above defined range, the resulting ink exhibitsexcellent printing properties and fastness to heat, giving good results.

The measurement of conductivity can be accomplished by an electrodemethod using a commercially available saturated potassium chloride.

The conductivity of the ink can be controlled mainly by theconcentration of ions in the aqueous solution. When the saltconcentration (ion concentration) is high, desalting may be effectedusing an ultrafiltration membrane or the like. Alternatively, theconductivity of the ink can be adjusted by the addition of variousorganic salts or inorganic salts.

Examples of the aforementioned inorganic salt for adjusting theconductivity of the ink include inorganic compound salts such aspotassium halide, sodium halide, sodium sulfate, potassium sulfate,sodium hydrogen sulfate, potassium hydrogen sulfate, sodium nitrate,sodium hydrogencarbonate, potassium hydrogencarbonate, sodium phosphate,dibasic sodium phosphate, sodium phosphate, potassium phosphatemonobasic and sodium dihydrogenphosphate.

Examples of the organic salt include organic salts such as sodiumacetate, potassium acetate, potassium tartrate, sodium tartrate, sodiumbenzoate, potassium benzoate, sodium p-toluenesulfonate, potassiumsaccharin, potassium phthalate and sodium picrate.

A surface active agent can be incorporated in the ink for ink jetrecording of the present invention to adjust the liquid physicalproperties of the ink, making it possible to provide the ink with anenhanced ejection stability and hence excellent effects such as enhancedwater resistance of image and prevention of running of ink printed.

Examples of the surface active agent employable herein include anionicsurface active agents such as sodium dodecylsulfate, sodiumdodecyloxysulfonate and sodium alkylbenzenesulfonate, cationic surfaceactive agents such as cetyl pyridinium chloride, trimethyl cetylammonium chloride and tetrabutylammonium chloride, and nonionic surfaceactive agents such as polyoxyethylene nonyl phenyl ether,polyoxyethylene naphthyl ether and polyoxy ethylene octyl phenyl ether.Particularly preferred among these surface active agents are nonionicsurface active agents.

The content of the surface active agent is preferably from 0.001% to 15%by weight, more preferably from 0.005% to 10% by weight, even morepreferably from 0.01% to 5% by weight based on the amount of the ink.

The ink for ink jet recording obtained in the present invention maycomprise properly selected additives incorporated therein in a properamount such as drying inhibitor for preventing the clogging of theejection nozzle with dried ink, penetration accelerator for helping theink to penetrate in the page, ultraviolet absorber, oxidation inhibitor,viscosity adjustor, surface tension adjustor, dispersant, dispersionstabilizer, antifungal agent, rust preventive, pH adjustor, anti-foamingagent and chelating agent.

As the drying inhibitor there is preferably used a water-soluble organicsolvent having a lower vapor pressure than water. Specific examples ofthe water-soluble organic solvent include polyvalent alcohols such asethylene glycol, propylene glycol, diethylene glycol, polyethyleneglycol, thiodiglycol, dithiodigycol, 2-methyl-1,3-propanediol,1,2,6-hexanetriol, acetylene glycol derivative, glycerin andtrimethylolpropane, lower alkylethers of polyvalent alcohol such asethylene glycol monomethyl (or ethyl) ether, diethylene glycolmonomethyl (or ethyl) ether and triethylene glycol monoethyl(orbutyl)ether, heterocyclic compounds such as 2-pyrrolidone,N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone andN-ethylmorpholine, sulfur-containing compounds such as sulfolane,dimethylsulfoxide and 3-sulfolene, polyfunctional compounds such asdiacetone alcohol and diethanolamine, and urea derivatives. Preferredamong these water-soluble organic solvents are polyvalent alcohols suchas glycerin and diethylene glycol. These drying inhibitors may be usedsingly or in combination of two or more thereof. These drying inhibitorsare preferably incorporated in the ink in an amount of from 10% to 50%by weight.

Examples of the penetration accelerator employable in the presentinvention include alcohols such as ethanol, isopropanol, butanol, di(tri) ethylene glycol monobutyl ether and 1,2-hexanediol, sodiumlaurylsulfate, sodium oleate, and nonionic surface active agents. Thesepenetration accelerators can exert a sufficient effect when incorporatedin the ink in an amount of from 10% to 30% by weight. These penetrationaccelerators are preferably used in an amount such that no printing runor print through occurs.

Examples of the ultraviolet absorber to be used to enhance thepreservability of the image in the present invention includebenzotriazole-based compounds as disclosed in JP-A-58-185677,JP-A-61-190537, JP-A-2-782, JP-A-5-197075 and JP-A-9-34057,benzophenone-based compounds as disclosed in JP-A-46-2784, JP-A-5-194483and U.S. Pat. No. 3,214,463, cinnamic acid-based compounds as disclosedin JP-B-48-30492, JP-A-56-21141 and JP-A-10-88106, triazine-basedcompounds as disclosed in JP-A-4-298503, JP-A-8-53427, JP-A-8-239368,JP-A-10-182621 and JP-T-8-50129, compounds as disclosed in ResearchDisclosure No. 24239, and compounds which absorb ultraviolet rays toemit fluorescence, i.e., so-called fluorescent brighteners, such asstilbene-based and benzoxazole-based compounds.

In the present invention, as the oxidation inhibitor to be used toenhance the image preservability there may be used any of variousorganic and metal complex-based discoloration inhibitors. Examples ofthe organic discoloration inhibitors include hydroquinones,alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes,chromans, alkoxyanilines, and heterocyclic compounds. Examples of themetal complex-based discoloration inhibitors include nickel complex, andzinc complex. Specific examples of these oxidation inhibitors includecompounds listed in the patents cited in Research Disclosure No. 18716,Articles VI-I and J, Research Disclosure No. 15162, Research DisclosureNo. 18716, left column, page 650, Research Disclosure No. 36544, page527, Research Disclosure No. 307105, page 872, and Research DisclosureNo. 15162, and compounds included in the formula and examples ofrepresentative compounds listed in JP-A-62-215272, pp. 127-137.

Examples of the antifungal agent to be incorporated in the presentinvention include sodium dehydroacetate, sodium benzoate, sodiumpyridinethione-1-oxide, ethyl p-hydroxybenzoate,1,2-benzoisothiazoline-3-one, and salts thereof. These antifungal agentsare preferably incorporated in the ink in an amount of from 0.02% to5.00% by weight.

For the details of these antifungal agents, reference can be made to“Bokin Bobizai Jiten (Dictionary of Anti-bacterial and AntifungalAgents)”, compiled by Dictionary Compilation Committee of The Societyfor Antibacterial and Antifungal Agents, Japan.

Examples of the rust preventive employable herein include acidicsulfites, sodium thiosulfate, ammonium thioglycolate,diisopropylammonium nitrite, pentaerthyritol tetranitrate,dicyclohexylammonium nitrite, and benzotriazole. These rust preventivesare preferably incorporated in the ink in an amount of from 0.02% to5.00% by weight.

The ink for ink jet recording to be used in the present invention ischaracterized in that it has a static surface tension of from 25 to 50mN/m, more preferably from 30 to 40 mN/m at 25° C. When the staticsurface tension of the ink exceeds 50 mN/m, the resulting ink exhibits adrastic deterioration in print quality such as ejection stability andresistance to running and whisker (e.g., when a black letter is printedon a cyan solid image, string-like running may extend from the blackletter) during color mixing. On the contrary, when the static surfacetension of the ink falls below 25 mN/m, the resulting ink can beattached to hard surface when ejected, causing defective printing.

Known examples of the static surface tension measuring method includecapillary rise method, dropping method, and ring method. In the presentinvention, as the static surface tension measuring method there is useda perpendicular plate method. The principle of the perpendicular platemethod will be described below.

When a thin glass or platinum plate is hanged partially dipped in aliquid, surface tension of the liquid acts downward along the length ofthe plate in contact with the liquid. The surface tension is measured bybalancing this force by a upward force.

The dynamic surface tension of the ink to be used in the presentinvention is preferably from 25 to 50 mN/m, more preferably from 30 to40 mN/m at 25° C. When the dynamic surface tension of the ink exceeds 50mN/m, the resulting ink exhibits a drastic deterioration in printquality such as ejection stability and resistance to running and whiskerduring color mixing. On the contrary, when the dynamic surface tensionof the ink falls below 25 mN/m, the resulting ink can be attached tohard surface when ejected, causing defective printing.

As the dynamic surface tension measuring methods there are knownvibration jet method, meniscus dropping method and maximum bubblepressure method as disclosed in “Shinjikken Kagaku Koza (New Instituteof Experimental Chemistry), 18th ed., Kaimen to Koroido (Interface andColloid)”, Maruzen, pp. 69-90 (1977). Further, a liquid film destructionmethod is known as disclosed in JP-A-3-2064. In the present invention,as the dynamic viscosity measuring method there is used a differentialbubble pressure method. The principle and method of effecting thismeasuring method will be described hereinafter.

When bubbles are formed in a solution which has been stirred touniformity, a new gas-liquid interface is produced. Surface active agentmolecules in the solution then gather on the surface of water at aconstant rate. The bubble rate (rate of formation of bubbles) ischanged. As the formation rate decreases, more surface active agentcomponents gather on the surface of bubbles, reducing the maximum bubblepressure shortly before the burst of bubbles. Thus, the maximum bubblepressure (surface tension) with respect to bubble rate can be detected.As a method for the measurement of dynamic surface tension there ispreferably used a method which comprises forming bubbles in a solutionusing a large probe and a small probe, measuring the differentialpressure of the two probes in the state of maximum bubble pressure, andthen calculating the dynamic surface tension from the differentialpressure.

The static surface tension and dynamic surface tension can be adjustedto the above defined range by using a surface tension adjustor.

As the surface tension adjustor there may be used a nonionic, cationicor anionic surface active agent. Examples of the anionic surface activeagent include aliphatic acid salts, alkylsulfuric acid esters,alkylarylsulfonates (e.g., alkylbenzenesulfonate, petrosulfonate),dialkylsulfosuccinates, alkylphosphoric acid esters, naphthalenesulfonicacid-formalin condensates, and polyoxyethylenealkylsulfuric acid esters.Examples of the nonionic surface active agent include acetylene-baseddiols (e.g., 2,4,7,9-tetramethyl-5-decyne-4,7-diol),polyoxyethylenealkyl ethers (e.g., polyoxyethylene decyl ether, ethyleneoxide adduct of acetylene-based diol), polyoxyethylenealiphatic acidesters, sorbitanaliphatic acid esters, polyoxyethylenesorbitanaliphaticacid esters, polyoxyethylenealkylamines, glycerinaliphatic acid esters,and oxyethyleneoxypropylene block copolymers.

Further, amine oxide-based amphoteric surface active agents such asN,N-dimethyl-N-alkylamine oxide may be used. Those listed as surfaceactive agents in JP-A-59-157, 636, pp. 37-38, and Research DisclosureNo. 308119 (1989) may be used.

An anionic surface active agent which has a two-chain hydrophobic moietyor a branched hydrophobic moiety, an anionic surface active agent havinga hydrophilic group in the vicinity of center of hydrophobic moiety, anonionic surface active agent which has a two-chain hydrophobic moietyor a branched hydrophobic moiety (e.g., one end ester-terminatedpolyoxide of 2-butyloctanoic acid, polyethylene oxide adduct ofundecane-6-ol) or a nonionic surface active agent having a hydrophilicgroup in the vicinity of center of hydrophobic moiety (e.g., ethyleneoxide adduct of acetylene-based diol (SURFYNOL Series (Air Products&Chemicals)) is preferred because they can be difficultly crystallizedor separated and cause little foamation. Preferred among these surfaceactive agents are those having a molecular weight of from not smallerthan 200 to not greater than 1,000, more preferably from not smallerthan 300 to not greater than 900, particularly from not smaller than 400to not greater than 900.

Such a surface tension adjustor is used preferably in an amount of from0.1 to 20% by weight, more preferably from 0.2 to 15% by weight based onthe weight of the ink.

The ink for ink jet recording of the present invention preferablycomprises a compound represented by the aforementioned formula (A)incorporated therein because the surface tension thereof can becontrolled without raising the foamability thereof.

wherein R¹ and R² each independently represent a saturated hydrocarbonhaving from 2 to 20 carbon atoms (e.g., ethyl, n-butyl, i-butyl,n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-dodecyl, n-hexadecyl,n-octadecyl), preferably a saturated hydrocarbon having from 4 to 13carbon atoms, more preferably a saturated hydrocarbon satisfying therequirement that the sum of the number of carbon atoms in R¹ and R² isfrom 8 to 18; and m represents an integer of from 2 to 40, preferablyfrom 4 to 30, more preferably from 4 to 20.

The compound represented by the formula (A) can be obtained by themethod described in Takehiko Fujimoto, “Shin Kaimen Kasseizai Nyumon(New Introduction to Surface Active Agents)”, total edition, page 107,1992, but it goes without saying that m in the formula (1) indicates anaverage value depending on the starting synthesis material and synthesismethod. Two or more compounds (A) having different m values may be used.Alternatively, a mixture of these compounds may be used.

Specific examples of the compound represented by the formula (A) will begiven, but the present invention is not limited thereto. Exemplarycompound R¹ R² m 1 C₂H₅ C₄H₉ 3 2 C₂H₅ C₄H₉ 5 3 C₄H₉ C₆H₁₃ 9.5 4 C₆H₁₃C₈H₁₇ 5 5 C₆H₁₃ C₈H₁₇ 8 6 C₆H₁₃ C₈H₁₇ 10 7 C₆H₁₃ C₈H₁₇ 11.4 8 C₆H₁₃C₈H₁₇ 12.5 9 C₆H₁₃ C₈H₁₇ 15 10 C₂H₅ C₈H₁₇ 25 11 C₇H₁₅ C₉H₁₉ 14 12 C₇H₁₅C₉H₁₉ 15 13 C₇H₁₅ C₉H₁₉ 20 14 C₇H₁₅ C₉H₁₉ 25 15 C₈H₁₇ C₁₀H₂₁ 30 16C₁₀H₂₁ C₁₂H₂₅ 20 17 C₁₀H₂₁ C₁₂H₂₅ 25 18 C₁₀H₂₁ C₁₃H₂₇ 20 20 C₁₀H₂₁C₁₃H₂₇ 25 21 C₁₀H₂₁ C₁₃H₂₇ 40

The compound represented by the formula (A) is incorporated in the inkpreferably in an amount of from 0.1 to 20% by weight, more preferablyfrom 0.2 to 15% by weight, even more preferably from 0.5 to 10% byweight.

The ink for ink jet recording of the present invention preferablycomprises a compound represented by the aforementioned formula (B)incorporated therein.

wherein R²¹, R²², R²³ and R²⁴ each independently represent an alkylgroup having from 1 to 6 carbon atoms; and n₁ and n₂ each represent anumber satisfying the requirement that the sum of n₁ and n₂ is from 0 to40.

The incorporation of the aforementioned compound makes it possible tocontrol the surface tension without raising the formability of the ink,giving good results.

The content of the compound represented by the aforementioned formula(B) is preferably from 0.1 to 20% by weight, more preferably from 0.2 to15% by weight based on the weight of the ink.

The ink of the present invention exhibits a viscosity of from 1 to 20mPa·s, more preferably from 2 to 15 mPa·s, particularly from 2 to 10mPa·s at 25° C. When the viscosity of the ink exceeds 30 mPa·s, theresulting recorded image can be fixed at a reduced rate. Further, theresulting ink exhibits a deteriorated ejectability. On the contrary,when the viscosity of the ink falls below 1 mPa·s, the resultingrecorded image runs and thus exhibits a reduced quality.

For the details of the method for the measurement of viscosity ofliquid, reference can be made to JIS Z8803. In practice, however, theviscosity of liquid can be simply measured using a commerciallyavailable viscometer. Examples of the rotary viscometer include Type Bviscometer and Type E viscometer produced by Tokyo Keiki Kogyo K. K. Inthe present invention, a Type VM-100A-L vibration viscometer (producedby YAMAICHI ELECTRONICS CO., LTD.) was used to measure viscosity at 25°C. The unit of viscosity is Pa·s. In practice, however, mPa·s is used.

The adjustment of viscosity can be arbitrarily carried out bycontrolling the added amount of the ink solvent. Examples of the inksolvent employable herein include glycerin, diethylene glycol,triethanolamine, 2-pyrrolidone, diethylene glycol monobutyl ether, andtriethylene glycol monobutyl ether.

The added amount of the ink solvent is preferably from 5 to 70% byweight, more preferably from 10 to 60% by weight based on the weight ofthe ink for ink jet recording. Two or more ink solvents may be used incombination.

Further, a viscosity adjustor may be used in the present invention.Examples of the viscosity adjustor employable herein include celluloses,water-soluble polymers such as polyvinylalcohol, and nonionic surfaceactive agents. For the details of these viscosity adjustors, referencecan be made to “Nendo Chousei Gijutsu (Technology for Preparation ofViscosity)”, Gijutsu Joho Kyoukai, Article 9, 1999, and “Inku JettoPurintayou Kemikaruzu (98 zouho)—Zairyou no Kaihatsu Doko/Tenbo Chousa(Chemicals for Ink Jet Printer (98 enlarged edition)—Research on Trendand View of Development of Materials)”, CMC, pp. 162-174, 1997.

The ink of the present invention is characterized in that it showsviscosity change of not greater than 250% from at 25° C. to at 10° C.and a surface tension change of not greater than 130% from at 25° C. toat 10° C. When the viscosity change from at 25° C. to at 10° C. exceeds250% or the surface tension change from at 25° C. to at 10° C. exceeds130%, the resulting ink shows a drastically deteriorated ejectionstability. In order to obtain stable ejection properties even in variousatmospheres, it is very important that the change of physical propertiesof the ink is as small as possible. In particular, the viscosity andsurface tension must be closely controlled.

The viscosity change from at 25° C. to at 10° C. is preferably notgreater than 200%, more preferably not greater than 190%, and thesurface tension change from at 25° C. to at 10° C. is preferably notgreater than 125%, more preferably not greater than 120%.

In the present invention, for the calculation of the viscosity changefrom at 25° C. to at 10° C. and the surface tension change from at 25°C. to at 10° C., the following equations are used.% Viscosity change from at 25° C. to at 100° C.=(Viscosity at 10°C./viscosity at 25° C.)×100 (%)% Surface tension change from at 25° C. to at 10° C.=(Surface tension at10° C./surface tension at 25° C.)×100 (%)

In the present invention, the change of viscosity or surface tension ofthe ink can be easily adjusted by adjusting the kind or amount of thewater-miscible organic solvent and surface active agent to beincorporated. Alternatively, in order to adjust the change of viscosityor surface tension, the following viscosity adjustor or surface tensionadjustor for adjusting viscosity or surface tension can be used.

For the details of the method for the measurement of viscosity ofliquid, reference can be made to JIS Z8803. In practice, however, theviscosity of liquid can be simply measured using a commerciallyavailable viscometer. Examples of the rotary viscometer include Type Bviscometer and Type E viscometer produced by Tokyo Keiki Kogyo K.K. Inthe present invention, a Type VM-100A-L vibration viscometer (producedby YAMAICHI ELECTRONICS CO., LTD.) was used to measure viscosity at 25°C. The unit of viscosity is Pa·s. In practice, however, mPa·s is used.

The ink of the present invention exhibits a viscosity of from 1 to 30mPa·s, more preferably from 2 to 15 mPa·s, particularly from 2 to 10mPa·s at 25° C. When the viscosity of the ink exceeds 30 mPa·s, theresulting recorded image can be fixed at a reduced rate. Further, theresulting ink exhibits a deteriorated ejectability. On the contrary,when the viscosity of the ink falls below 1 mPa·s, the resultingrecorded image runs and thus exhibits a reduced quality.

The adjustment of viscosity can be arbitrarily carried out bycontrolling the added amount of the ink solvent. Examples of the inksolvent employable herein include glycerin, diethylene glycol,triethanolamine, 2-pyrrolidone, diethylene glycol monobutyl ether, andtriethylene glycol monobutyl ether.

The added amount of the ink solvent for adjusting viscosity ispreferably from 5 to 70% by weight, more preferably from 10 to 60% byweight based on the weight of the ink for ink jet recording. Two or moreink solvents may be used in combination.

Further, as other viscosity adjustors there may be used, e.g.,celluloses, water-soluble polymers such as polyvinyl alcohol, andnonionic surface active agents. For the details of these viscosityadjustors, reference can be made to “Nendo Chousei Gijutsu (Technologyfor Preparation of Viscosity)”, Gijutsu Joho Kyoukai, Article 9, 1999,and “Inku Jetto Purintayou Kemikaruzu (98 zouho)—Zairyou no KaihatsuDoko/Tenbo Chousa (Chemicals for Ink Jet Printer (98 enlargededition)—Research on Trend and View of Development of Materials)”, CMC,pp. 162-174, 1997.

The ink of the present invention may comprise a pH adjustor incorporatedtherein. The pH value of the ink solution is preferably from 4 to 12,more preferably from 5 to 10, particularly from 6 to 9.

For the measurement of pH, a commercially available test paper may beused. Alternatively, the measurement of pH can be made by using anelectrode method using saturated potassium chloride.

The adjustment of pH can be accomplished by the addition of a basiccompound or acidic compound. In any case, both inorganic and organiccompounds may be used.

Examples of the basic compounds employable herein include inorganiccompounds such as sodium hydroxide, potassium hydroxide, sodiumcarbonate, potassium carbonate, sodium hydrogencarbonate, potassiumhydrogencarbonate, sodium acetate, potassium acetate, sodium phosphateand sodium phosphate dibasic, and organic bases such as aqueous ammonia,methylamine, ethylamine, diethylamine, triethylamine, ethanolamine,diethanolamine, triethanolamine, ethylenediamine, piperidine,diazabicycloctane, diazabicycloudecene, pyridine, quinoline, picoline,lutidine and collidine.

Examples of the acidic compounds employable herein include inorganiccompounds such as hydrochloric acid, sulfuric acid, phosphoric acid,boric acid, sodium hydrogensulfate, potassium hydrogensulfate, potassiumdihdyrogenphosphate and sodium dihydrogenphosphate, and organiccompounds such as acetic acid, tartaric acid, benzoic acid,trifluoroacetic acid, methanesulfonic acid, ethanesulfonic acid,methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid,saccharinic acid, phthalic acid, picric acid and quinolinic acid.

In the present invention, as dispersant and dispersion stabilizer theremay be used the aforementioned various cationic, anionic and nonionicsurface active agents as necessary. As the anti-forming agent there maybe used a fluorine-based or silicone-based compound or a chelating agentsuch as EDTA as necessary.

For the details of the method for the preparation of an aqueous ink forink jet recording, reference can be made to JP-A-5-148436,JP-A-5-295312, JP-A-7-97541, JP-A-7-82515, JP-A-7-118584, JapanesePatent Application No. 2000-200780 and Japanese Patent Application No.2000-249799. These methods can apply also to the preparation of the inkfor ink jet recording of the present invention.

The process for the production of an ink for ink jet recording of thepresent invention comprises dissolving and/or dispersing at least onedye represented by the aforementioned formula (I) in a medium,characterized in that there is provided at least a step of applyingultrasonic vibration.

In the present invention, in order to prevent the ink from bubblingunder pressure applied in the recording head, sound energy equal to orhigher than the energy given in the recording head is applied at thestep of producing ink to remove bubbles.

The ultrasonic vibration comprises an ultrasonic wave having a frequencyof not smaller than 20 kHz, preferably not smaller than 40 kHz, morepreferably 50 kHz. The energy which is applied to the solution byultrasonic vibration is normally not smaller than 2×107 J/m³, preferablynot smaller than 5×107 J/m³, more preferably not smaller than 1×108J/m³. The time during which ultrasonic vibration is given is normallyfrom about 10 minutes to 1 hour.

The step of applying ultrasonic vibration may be effected at any timeafter the addition of dyes to the medium to exert desired effects. Thedesired effects can be exerted also when the ink thus completed is givenultrasonic vibration after storage. However, ultrasonic vibration ispreferably applied during the dissolution and/or dispersion of dyes inthe medium to exert a greater effect of removing bubbles and acceleratethe dissolution and/or dispersion of the dyes in the medium.

In other words, the aforementioned step of applying at least ultrasonicvibration may be effected either during or after the step of dissolvingand/or dispersing the dyes in the medium. In some detail, the step ofapplying at least ultrasonic vibration may be arbitrarily effected onceor more times during the period between the preparation of the ink andthe completion of the product.

In the present invention, the step of dissolving and/or dispersing thedyes in the medium preferably comprises a step of dissolving the dyes ina part of the medium and a step of mixing the solution with theremaining portion of the medium. More preferably, ultrasonic vibrationis applied at at least one of the aforementioned steps. Even morepreferably, at least ultrasonic vibration is applied at the step ofdissolving the dyes in a part of the medium.

The aforementioned step of mixing the solution with the remainingportion of the medium may comprise a single step or a plurality ofsteps.

Further, heat deaeration or vacuum deaeration is preferably effectedadditionally in the ink production according to the present invention toenhance the effect of removing bubbles from the ink. The heat deaerationstep or vacuum deaeration step is preferably effected at the same timewith or after the step of mixing the solution with the remaining portionof the medium.

As a means of generating ultrasonic vibration at the step of applyingultrasonic vibration there may be used a known apparatus such asultrasonic dispersing machine.

In the present invention, as the medium there is preferably used wateror an aqueous medium which is a mixture of water and a water-miscibleorganic solvent.

In the process for the preparation of the ink of the present invention,it is important to effect a step of removing dust as solid content byfiltration after the dissolution or dispersion of the phthalocyanine dyerepresented by the aforementioned formula (I) in the aqueous medium forthe preparation of the ink. For this job, a filter is used. As such afilter there is used a filter having an effective pore diameter of notgreater than 1 μm, preferably from not smaller than 0.05 μm to notgreater than 0.3 μm, particularly from not smaller than 0.25 μto notgreater than 0.3 μm. As the filter material there may be used any ofvarious known materials. In the case where a water-soluble dye ink isused, a filter prepared for aqueous solvent is preferably used. Inparticular, a filter made of a polymer material which can difficultlygive dust is preferably used. Filtration may be accomplished by pumpingthe solution through the filter or may be effected under pressure orreduced pressure.

Filtration is often accompanied by the entrapment of air in thesolution. Bubbles due to air thus entrapped can often cause disturbancein image in the ink jet recording. Thus, the deaeration step ispreferably provided separately. Deaeration may be accomplished byallowing the solution thus filtered to stand or by the use of variousmethods such as ultrasonic deaeration and vacuum deaeration using acommercially available apparatus. The ultrasonic deaeration may beeffected preferably for about 30 seconds to 2 hours, more preferably forabout 5 minutes to 1 hour.

These jobs are preferably effected in a space such as clean room andclean bench to prevent the contamination by dust. In the presentinvention, these jobs are preferably effected in a space having acleanness degree of not greater than 1,000 class. The term “cleannessdegree” as used herein is meant to indicate the value measured by a dustcounter.

The recording paper and recording film to be used in the ink jetrecording method of the present invention will be described hereinafter.As the support in the recording paper or recording film there may beused one obtained by processing a chemical pulp such as LBKP and NBKP, amechanical pulp such as GP, PGW, RMP, TMP, CTMP, CMP and CGP, used paperpulp such as DIP or the like, optionally mixed with known additives suchas pigment, binder, sizing agent, fixing agent, cationic agent and paperstrength improver, through various paper machines such as foundrinierpaper machine and cylinder paper machine. As the support there may beused either a synthetic paper or plastic film sheet besides thesesupport materials. The thickness of the support is preferably from 10 μmto 250 μm. The basis weight of the support is preferably from 10 to 250g/m².

An image-receiving layer and a back coat layer may be provided on thesupport directly or with a size press or anchor coat layer of starch,polyvinyl alcohol or the like interposed therebetween to prepare animage-receiving material. The support may be further subjected toleveling using a calendering machine such as machine calender, TGcalender and soft calender.

In the present invention, as the support there is preferably used apaper or plastic film laminated with a polyolefin (e.g., polyethylene,polystyrene, polybutene, copolymer thereof) or polyethyleneterephthalate on both sides thereof. The polyolefin preferably comprisesa white pigment (e.g., titanium oxide, zinc oxide) or a tinting dye(e.g., cobalt blue, ultramarine, neodymium oxide) incorporated therein.

The image-receiving layer to be provided on the support comprises aporous material or aqueous binder incorporated therein. Theimage-receiving layer also preferably comprises a pigment incorporatedtherein. As such a pigment there is preferably used a white pigment.Examples of the white pigment employable herein include inorganic whitepigments such as calcium carbonate, kaolin, talc, clay, diatomaceousearth, synthetic amorphous silica, aluminum silicate, magnesiumsilicate, calcium silicate, aluminum hydroxide, alumina, lithopone,zeolite, barium sulfate, calcium sulfate, titanium dioxide, zinc sulfateand zinc carbonate, and organic pigments such as styrene-based pigment,acrylic pigment, urea resin and melamine resin. Particularly preferredamong these pigments are porous inorganic white pigments. In particular,synthetic amorphous silica having a large pore area, etc. are preferred.As the synthetic amorphous silica there may be also used anhydroussilicate obtained by dry method (gas phase method) or hydrous silicateobtained by wet method.

Specific examples of the recording paper comprising the aforementionedpigments incorporated in the image-receiving layer include thosedisclosed in JP-A-10-81064, JP-A-10-119423, JP-A-10-157277,JP-A-10-157277, JP-A-10-217601, JP-A-11-348409, JP-A-2001-138621,JP-A-2000-43401, JP-A-2000-211235, JP-A-2000-309157, JP-A-2001-96897,JP-A-2001-138627, JP-A-11-91242, JP-A-8-2087, JP-A-8-2090, JP-A-8-2091,JP-A-8-2093, JP-A-8-2093, JP-A-174992, JP-A-11-192777, andJP-A-2001-301314.

Examples of the aqueous binder to be incorporated in the image-receivinglayer include water-soluble polymers such as polyvinyl alcohol,silanol-modified polyvinyl alcohol, starch, cationated starch, casein,gelatin, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinylpyrrolidone, polyalkylene oxide and polyalkylene oxide derivative, andwater-dispersible polymers such as styrene butadiene latex and acrylemulsion. These aqueous binders may be used singly or in combination oftwo or more thereof. In the present invention, particularly preferredamong these aqueous binders are polyvinyl alcohol and silanol-modifiedpolyvinyl alcohol from the standpoint of adhesion to pigment andexfoliation resistance of ink-receiving layer.

The ink-receiving layer may comprise a mordant, a waterproofing agent, alight-resistance improver, a gas resistance improver, a surface activeagent, a film hardener and other additives incorporated therein besidesthe pigments and aqueous binders.

The mordant to be incorporated in the image-receiving layer ispreferably passivated. To this end, a polymer mordant is preferablyused.

For the details of the polymer mordant, reference can be made toJP-A-48-28325, JP-A-54-74430, JP-A-54-124726, JP-A-55-22766,JP-A-55-142339, JP-A-60-23850, JP-A-60-23851, JP-A-60-23852,JP-A-60-23853, JP-A-60-57836, JP-A-60-60643, JP-A-60-118834,JP-A-60-122940, JP-A-60-122941, JP-A-60-122942, JP-A-60-235134,JP-A-1-161236, U.S. Pat. Nos. 2,484,430, 2,548, 564, 3, 148,061,3,309,690, 4,115,124, 4,124,386, 4,193,800, 4,273,853, 4,282,305 and4,450,224. An image-receiving material containing a polymer mordantdisclosed in JP-A-1-161236, pp. 212 to 215 is particularly preferred.The use of the polymer mordant disclosed in the above cited patent makesit possible to obtain an image having an excellent quality and henceimprove the light-resistance of the image.

The waterproofing agent can be used to render the image waterproof. Assuch a waterproofing agent there is preferably used a cationic resin inparticular. Examples of such a cationic resin include polyamidepolyamine epichlorohydrin, polyethylenimine, polyamine sulfone, dimethyldiallyl ammonium chloride polymer, and cation polyacrylamide. Thecontent of such a cationic resin is preferably from 1% to 15% by weight,particularly from 3% to 10% by weight based on the total solid contentof the ink-receiving layer.

Examples of the light-resistance improver and gas resistance improverinclude phenol compounds, hindered phenol compounds, thioethercompounds, thiourea compounds, thiocyanic acid compounds, aminecompounds, hindered amine compounds, TEMPO compounds, hydrazinecompounds, hydrazide compounds, amidine compounds, vinyl-containingcompounds, ester compounds, amide compounds, ether compounds, alcoholcompounds, sulfinic acid compounds, saccharides, water-soluble reducingcompounds, organic acids, inorganic acids, hydroxyl-containing organicacids, benzotriazole compounds, benzophenone compounds, triazinecompounds, heterocyclic compounds, water-soluble metal salts, organicmetal compounds, and metal complexes.

Specific examples of these compounds include those disclosed inJP-A-10-182621, JP-A-2001-260519, JP-A-2000-260519, JP-B-4-34953,JP-B-4-34513, JP-B-4-34512, JP-A-11-170686, JP-A-60-67190,JP-A-7-276808, JP-A-2000-94829, JP-T-8-512258, and JP-A-11-321090.

The surface active agent acts as a coating aid, releasability improver,slipperiness improver or antistat. For the details of the surface activeagent, reference can be made to JP-A-62-173463 and JP-A-62-183457.

An organic fluoro-compounds may be used instead of the surface activeagent. The organic fluoro-compound is preferably hydrophobic. Examplesof the organic fluoro-compound include fluorine-based surface activeagents, oil-based fluorine compounds (e.g., fluorine-based oil), andsolid fluorine-based compound resins (e.g., tetrafluoroethylene resin).For the details of the organic fluoro-compound, reference can be made toJP-B-57-9053 (8th to 17th columns), JP-A-61-20994, and JP-A-62-135826.

As the film hardener there may be used any of materials disclosed inJP-A-1-161236, page 222, JP-A-9-263036, JP-A-10-119423, andJP-A-2001-310547.

Other examples of additives to be incorporated in the image-receivinglayer include pigment dispersants, thickening agents, antifoamingagents, dyes, fluorescent brighteners, preservatives, pH adjustors,matting agents, and film hardeners. There may be provided one or twoink-receiving layers.

The recording paper and recording film may comprise a back coat layerprovided thereon. Examples of the components which can be incorporatedin the back coat layer include white pigments, aqueous binders, andother components.

Examples of the white pigments to be incorporated in the back coat layerinclude inorganic white pigments such as light calcium carbonate, heavycalcium carbonate, kaolin, talc, calcium sulfate, barium sulfate,titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white,aluminum silicate, diatomaceous earth, calcium silicate, magnesiumsilicate, synthetic amorphous silica, colloidal silica, colloidalalumina, pseudo-boehmite, aluminum hydroxide, alumina, lithopone,hydrated halloysite, magnesium carbonate and magnesium hydroxide, andorganic pigments such as styrene-based plastic pigment, acrylic plasticpigment, polyethylene, microcapsule, urea resin and melamine resin.

Examples of the aqueous binder to be incorporated in the back coat layerinclude water-soluble polymers such as styrene/maleate copolymer,styrene/acrylate copolymer, polyvinyl alcohol, silanol-modifiedpolyvinyl alcohol, starch, cationated starch, casein, gelatin,carboxymethyl cellulose, hydroxyethyl cellulose andpolyvinylpyrrolidone, and water-dispersible polymers such asstyrenebutadiene latex and acryl emulsion. Examples of other componentsto be incorporated in the back coat layer include antifoaming agents,foaming inhibitors, dyes, fluorescent brightening agents, preservatives,and waterproofing agents.

The layers (including back layer) constituting the ink jet recordingpaper and film may comprise a fine dispersion of polymer incorporatedtherein. The fine dispersion of polymer is used for the purpose ofimproving physical properties of film, e.g., stabilizing dimension,inhibiting curling, adhesion and film cracking. For the details of thefine dispersion of polymer, reference can be made to JP-A-62-245258,JP-A-62-1316648, and JP-A-62-110066. The incorporation of a finedispersion of polymer having a glass transition temperature as low asnot higher than 40° C. in a layer containing a mordant makes it possibleto prevent the cracking or curling of the layer. The incorporation of afine dispersion of polymer having a high glass transition temperature,too, in the back layer makes it possible to prevent the curling of theback layer.

In the present invention, the ink jet recording method is not limited.The ink of the present invention may be used in any known recordingmethod such as electrostatic control method which utilizes electrostaticattraction to eject ink, drop-on-demand method (pressure pulse method)utilizing vibrational pressure of piezoelectric element, acoustic inkjet method which comprises converting electrical signal to acoustic beamwith which the ink is irradiated to produce a radiation pressure that isutilized to eject the ink and thermal ink jet (bubble jet) method whichcomprises heating the ink to form bubbles that raise the pressure toeject the ink.

Examples of the ink jet recording method include a method whichcomprises ejecting many portions of an ink having a low concentrationcalled photoink in a small volume, a method which comprises using aplurality of inks having substantially the same hue but differentdensities to improve the image quality, and a method involving the useof a colorless transparent ink.

EXAMPLE

The present invention will be further described in the followingexamples, but the present invention is not limited thereto.

Examples of viscosity:

Examples 1 to 3 Example 1

To the following components was added deionized water to make 1 l. Themixture was then heated to a temperature of from 30° C. to 40° C. withstirring for 1 hour. Thereafter, the solution was adjusted to pH 9 witha 10 mol/l KOH, closely adjusted to a viscosity of 6 mPa·sec withglycerin and water, and then filtered through a microfilter having anaverage pore diameter of 0.25 μm under reduced pressure to prepare alight cyan ink solution. Cyan dye of the present invention 17.5 g/l(Exemplary Compound 154) Diethylene glycol 164 g/l Glycerin 123 g/lTriethylene glycol monobutyl ether 119 g/l Triethanolamine 6.5 g/lBenzotriazole 0.07 g/l PROXEL XL2 3.5 g/l Surface active agent (w-1) 10g/l

Further, cyan, light magenta, magenta, yellow and black inks wereprepared in the same manner as used in the light cyan ink except thatthe dye additive was changed and the viscosity of the inks wereuniformly adjusted to 6 mPa·sec by close adjustment of the amount ofglycerin and water. The ink set 101 shown in Table 1 was thus prepared.TABLE 1 Light Light cyan Cyan magenta Magenta Yellow Black Dye (g/l) 154154 A-1 A-1 A-4 A-55 17.5 68.0 10.2 30.8 28.0 20.0 A-6 39.0 A-7 17.0 A-320.0 Diethylene 164 107 150 110 160 20 gyclol (g/l) Urea (g/l) — — 37 46— — Glycerin (g/l) 123 110 130 160 150 120 Triethylene 119 127 130 140130 — glycol monobutyl ether (g/l) Diethylene — — — — — 230 glycolmonobutyl ether (g/l) 2-Pyrrolidone — 20 40 — — 80 (g/l) Surface active10 10 6 12 3 5 agent (g/l) Triethanolamine 6.5 10 7 7 1 18 (g/l)Benzotriazole 0.07 0.09 0.07 0.08 0.06 0.08 (g/l) Proxel XL2 (g/l) 1.04.0 5.0 4.5 3 4 Deionized water added to make 1 l A-1

A-2

A-3

A-4

A-5

A-6

A-7

As a surface active agent there was used W-1 as shown below.

Ink sets 102 to 109 were then prepared in the same manner as in the inkset 101 except that the kind of dyes incorporated in the light cyan andcyan inks were changed and the viscosity of these inks were changed asset forth in Table 2 with glycerin and water. The light magenta,magenta, yellow and black inks incorporated in the ink sets 102 to 109comprised the same kind of dyes as in the ink set 101 and had the sameviscosity as in the ink set 101. TABLE 2 Ink set Light cyan Cyan Remarks101 Dye 154 154 Inventive Viscosity 6 mPa · sec 6 mPa · sec 102 Dye 154154 Inventive Viscosity 6 mPa · sec 6 mPa · sec 103 Dye 154 154Inventive Viscosity 4 mPa · sec 6 mPa · sec 104 Dye 154 154 InventiveViscosity 10 mPa · sec 6 mPa · sec 105 Dye 154 154 Inventive Viscosity 5mPa · sec 10 mPa · sec 106 Dye 154 154 Comparative Viscosity 30 mPa ·sec 4 mPa · sec 107 Dye 154 154 Comparative Viscosity 30 mPa · sec 30mPa · sec 108 Dye 154 154 Comparative Viscosity 0.8 mPa · sec 0.8 mPa ·sec 109 Dye A-2 A-2 Comparative Viscosity 6 mPa · sec 6 mPa · sec

Subsequently, the foregoing ink sets 101 to 109 were each packed in thecartridge of a Type PM800C ink jet printer (produced by EPSON CO., LTD.)by which an image was then printed on a Type EX ink jet photographicgloss paper (produced by Fuji Photo Film Co., Ltd.) to evaluate thefollowing properties. For the evaluation of “printing property (1)”, thecartridge was mounted on the printer. The ejection of ink from all thenozzles was then confirmed. Printing was then made on 20 sheets of A4size paper. The print was then evaluated for disturbance.

-   -   A: No print disturbance during the period between the beginning        and the end of printing;    -   B: Occurrence of output with print disturbance;    -   C: Print disturbance during the period between the beginning and        the end of printing.

For the evaluation of “printing properties (2)”, the cartridge wasallowed to stand at 60° C. for 2 days. The print was then evaluated fordisturbance in the same manner as in “printing properties (1)”.

For the evaluation of “dryability”, the print was immediately touchedwith a finger which was then visually observed for stain.

Referring to running of fine line, fine line patterns were printed withyellow, magenta, cyan and black inks, respectively. These fine linepatterns were each then visually evaluated for “running of fine line(1)”. For the evaluation of black ink, a fine line was printed with ablack ink on a solid print of magenta ink. “Running of fine line (2)”due to contact of two color inks was evaluated as well.

For the evaluation of “water resistance”, the image thus obtained wasdipped in deionized water for 10 seconds, and then evaluated forrunning.

For the evaluation of image preservability, a solid cyan image printsample was prepared. The sample was then evaluated as follows.

For the evaluation of “light-fastness”, the print which had been madewas immediately measured for image density Ci by means of a reflectiondensitometer (X-Rite 310TR), irradiated with light from a xenon lamp(85,000 lux) using a weatherometer produced by Atlas Electric Devices,Inc. for 7 days, and then again measured for image density Cf todetermine the dye remaining ratio (Ci/Cf×100). The dye remaining ratiowas measured at three points of reflection density (1, 1.5, 2). Thoseshowing a dye remaining ratio of not smaller than 85% at any of thethree density points were defined as A, those showing a dye remainingratio of smaller than 85% at two of the three points were defined as B,and those showing a dye remaining ratio of smaller than 85% at all thethree density points were defined as C.

For the evaluation of heat fastness, the sample was stored underconditions of from 70 to 80% RH for 7 days. The sample was measured fordensity using a reflection densitometer (Type X-rite 310TR) before andafter storage to determine the dye remaining ratio which was thenevaluated. The dye remaining ratio was then evaluated at threereflection density points, i.e., 1, 1.5 and 2. Those showing a dyeremaining ratio of not smaller than 90% at any of the three densitypoints were defined as A. Those showing a dye remaining ratio of lessthan 90% at two of the three density points were defined as B. Thoseshowing a dye remaining ratio of less than 90% at all the density pointswere defined as C.

For the evaluation of “ozone resistance”, the sample was stored under80° C. heated conditions open to the atmosphere for 7 days. The samplewas measured for density using a reflection densitometer (Type X-rite310TR) before and after storage to determine the dye remaining ratiowhich was then evaluated. The dye remaining ratio was then evaluated atthree reflection density points, i.e., 1, 1.5 and 2. Those showing a dyeremaining ratio of not smaller than 90% at any of the three densitypoints were defined as A. Those showing a dye remaining ratio of lessthan 90% at two of the three density points were defined as B. Thoseshowing a dye remaining ratio of less than 90% at all the density pointswere defined as C.

The results thus obtained are set forth in Tables 3 and 4. TABLE 3Running Running Ink Printing Printing of fine of fine Water setproperties 1 properties 2 Dryability line 1 line 2 resistance 101 A A GG G G (good) 102 A A G G G G 103 A A G G G G 104 A A G G G G 105 A A G GG G 106 B A G G G G 107 C A P G G F (poor) 108 C C G P F G (fair) 109 AB G G G G

TABLE 4 Heat Gas Ink set Light-fastness fastness resistance Remarks 101A A A Inventive 102 A A A Inventive 103 A A A Inventive 104 A A AInventive 105 A A A Inventive 106 A A A Comparative 107 A A AComparative 108 A A A Comparative 109 B B C Comparative

It is made obvious that when the inks of the present invention are used,an excellent ejection stability can be obtained because they areexcellent in printing properties (1) and (2). It is made obvious thatthe inks of the present invention are excellent also in waterresistance, light-fastness and heat fastness. Further, the inks of thepresent invention show good running of a fine line with no bleeding.

Even when the image-receiving paper to be used in the present inventionis changed to PM photographic gloss paper produced by EPSON CO., LTD. orPR101, produced by Canon Inc., effects similar to the aforementionedresults can be exerted.

Example 2

The inks prepared in Example 1 were each packed in the cartridge of aType BJ-F850 ink jet printer (produced by Canon Inc.) by which an imagewas then printed on a Type EX ink jet photographic gloss paper (producedby Fuji Photo Film Co., Ltd.) to effect evaluation in the same manner asin Example 1. Results similar to that of Example 1 were obtained. Evenwhen the image-receiving paper was changed to PM photographic glosspaper produced by EPSON CO., LTD. or PR101, produced by Canon Inc.,effects similar to the aforementioned results were exerted.

Example 3

7 g of a dye (Exemplary Compound 189) and 4 g of sodiumdioctylsulfosuccinate were dissolved in a mixture of 6 g of a highboiling solvent (s-1), 10 g of a high boiling organic solvent (s-2) and50 ml of ethyl acetate at 70° C. To the solution was then added 500 mlof deionized water with stirring by a magnetic stirrer to prepare anoil-in-water type coarse dispersion.

Subsequently, the coarse dispersion was passed through a microfluidizer(MICROFLUIDX INC.) at a pressure of 60 MPa five times to undergoatomization. The emulsion thus prepared was then subjected todesolvation using a rotary evaporator until it was free of odor of ethylacetate.

To the fine emulsion of oil-soluble dye thus obtained were then added140 g of diethylene glycol, 64 g of glycerin, 13 g of a surface activeagent (w-1), and additives such as urea. To the mixture was then added900 ml of deionized water. The solution was then adjusted to pH9 with a10 mol/l KOH. The viscosity of the solution was then adjusted byadjusting the amount of glycerin and water to prepare a light cyan inkaccording to Table 16. The emulsion-dispersed ink thus obtained was thenmeasured for volume-average particle size using a Type UPA microtrack(NIKKISO CO., LTD.). The result was 58 nm.

Further, magenta, light magenta, cyan, yellow and black inks of the inkset 201 set forth in Table 5 were prepared in the same manner asdescribed above except that the kind of dyes and high boiling organicsolvents to be used were changed. TABLE 1 Light Light cyan Cyan magentaMagenta Yellow Black Dye (g/l) 189 189 M-1 M-1 Y-3 C-2 7.0 35.0 5.0 20.028.0 19.0 M-1 10.0 Y-3 14.0 High boiling S-1 6.0 25.0 4.0 14.0 20.0 30.0organic solvent S-2 10.0 45.0 6.0 25.0 35.0 53.0 (g/l) Sodium 4.0 30.06.2 23.0 35.0 52.0 dioctylsulfo- succinate (g/l) Diethylene 140 140 130140 130 120 gyclol (g/l) Urea (g/l) 46.0 46.0 46.0 46.0 46.0 46.0Glycerin (gIl) 64.0 64.0 64.0 64.0 64.0 64.0 Triethanol- amine (g/l) 1010 10 10 10 10 Benzotriazole 0.08 0.08 0.08 0.08 0.08 0.08 (g/l) Surfaceactive 13 13 13 13 13 13 agent W-1 (g/l) Proxel XL2 (g/l) 3.5 3.5 3.53.5 3.5 3.5 Deionized water added to make 1 l Volume average 58 nm 65 nm50 nm 55 nm 60 nm 70 nm particle size M-1

C-2

Y-3

S-1

S-2

Ink sets 202 to 208 were similarly prepared according to Table 17without changing the formulation of magenta, light magenta, yellow andblack inks.

The added amount of the compound of the present invention was 2.0% byweight each for the various inks.

A comparative ink set 209 was then prepared in the same manner as theink set 201 except that the kind of dye was changed to C-2.Subsequently, these ink sets 201 to 209 were each packed in thecartridge of a Type PM770C ink jet printer (produced by EPSON CO., LTD.)by which an image was then printed on a Type EX ink jet photographicgloss paper (produced by Fuji Photo Film Co., Ltd.) to effect evaluationin the same manner as in Example 1. The results thus obtained are setforth in Table 6. TABLE 6 Running of Running of Viscosity EjectionLight- Gas Water fine line fine line Ink set Dye mPa · sec stabilityfastness resistance resistance (1) (2) Remarks 201 189 5 A A A A G GInventive (good) 202 189 3 A A A A G G Inventive 203 189 10 A A A A G GInventive 204 182 4 A A A A G G Inventive 205 180 4 A A A A G GInventive 206 187 5 A A A A G G Inventive 207 189 30 B A A A G GComparative 208 189 0.8 C A A A P F Comparative (poor) (fair) 209 C-2 5A A B A G G Comparative

It is made obvious that the inks of the present invention have anexcellent ejection stability and good weathering resistance(light-fastness and heat fastness, ozone resistance) and waterresistance and thus can provide a recorded image free of running fromfine line.

Example of conductivity:

Example 4

To the following components was added deionized water to make 1 l. Themixture was then heated to a temperature of from 30° C. to 40° C. withstirring for 1 hour. Thereafter, the solution was adjusted to pH 7.6with potassium hydroxide, and then filtered through a microfilter havingan average pore diameter of 0.25 μm under reduced pressure to prepare alight cyan ink solution.

(Components of Light Cyan Ink) Cyan dye of the present invention 17.5g/l (Exemplary Compound 154) Diethylene glycol 150 g/l Urea 37 g/lGlycerin 130 g/l Triethylene glycol monobutyl ether 130 g/lTriethanolamine 6.9 g/l Benzotriazole 0.08 g/l PROXEL KL2 3.5 g/lSurfynol STG 10 g/l

Further, to the aforementioned formulation was added 68 g of the cyandye (Exemplary Compound 154) to prepare a cyan ink solution. Inks (InkNos. 101 to 106) were prepared by adjusting the conductivity of the cyanand light cyan inks by the change of the amount of solvents (glycerin,triethylene glycol monobutyl ether, diethylene glycol) and the use oflithium chloride. Further, inks (Ink Nos. 107 to 109) were prepared byadjusting the conductivity of cyan and light cyan inks of PM-950Cproduced by EPOSON CO., LTD. The conductivity of these inks are setforth in Table 7. TABLE 7 Conductivity of light Conductivity of Ink No.cyan ink (S/m) cyan ink (S/m) 101 (comparative) 0.009 0.009 102(inventive) 0.027 0.026 103 (inventive) 0.452 0.542 104 (inventive)0.886 0.941 105 (inventive) 1.23 1.11 106 (comparative) 11.6 12.3 107(comparative) 0.319 0.432 108 (comparative) 0.852 0.839 109(comparative) 1.01 1.33 110 (comparative) 12.5 11.9

Subsequently, these Ink Nos. 101 to 110 were each packed in thecyan/light cyan portion of the cartridge of a Type PM770C ink jetprinter (produced by EPSON CO., LTD.) by which an image was then printedon a Type EX ink jet photographic gloss paper (produced by Fuji PhotoFilm Co., Ltd.) to evaluate ejection stability and image preservability.

For ejection stability, the following printing properties (1) and (2)were evaluated.

1) For the evaluation of printing properties (1), the cartridge wasmounted on the printer. The ejection of ink from all the nozzles wasthen confirmed. Printing was then made on 20 sheets of A4 size paper.The print was then evaluated for disturbance.

-   -   A: No print disturbance during the period between the beginning        and the end of printing;    -   B: Occurrence of output with print disturbance;    -   C: Print disturbance during the period between the beginning and        the end of printing.        2) For the evaluation of printing properties (2), the cartridge        was allowed to stand at 60° C. for 2 days. The print was then        evaluated for disturbance in the same manner as in “printing        properties (1)”.

For the evaluation of image preservability, a solid cyan image printsample was prepared. The sample was then evaluated as follows.

(1) Light-Fastness:

For the evaluation of light-fastness, the print which had been made wasimmediately measured for image density Ci by means of X-Rite 310,irradiated with light from a xenon lamp (85,000 lux) using aweatherometer produced by Atlas Electric Devices, Inc. for 10 days, andthen again measured for image density Cf to determine the dye remainingratio [Cf/Ci]×100. The dye remaining ratio was measured at three pointsof reflection density (1, 1.5, 2). Those showing a dye remaining ratioof not smaller than 70% at any of the three density points were definedas A, those showing a dye remaining ratio of smaller than 70% at two ofthe three points were defined as B, and those showing a dye remainingratio of smaller than 70% at all the three density points were definedas C.

(2) Heat Fastness:

For the evaluation of heat fastness, the sample was stored underconditions of 80° C. and 70% RH for 10 days. The sample was measured fordensity using X-rite 310 before and after storage to determine the dyeremaining ratio which was then evaluated. The dye remaining ratio wasthen evaluated at three reflection density points, i.e., 1, 1.5 and 2.Those showing a dye remaining ratio of not smaller than 90% at any ofthe three density points were defined as A. Those showing a dyeremaining ratio of less than 90% at two of the three density points weredefined as B. Those showing a dye remaining ratio of less than 90% atall the density points were defined as C. Those showing recognizeddiscoloration were defined as D.

(3) Ozone Resistance:

For the evaluation of ozone resistance, the aforementioned photographicgloss paper on which an image had been formed was allowed to stand in abox the ozone gas concentration of which had been adjusted to 0.5 ppmfor 7 days. The photographic gloss paper was measured for image densityusing a reflection densitometer (X-Rite 310TR) before and after aging todetermine the dye remaining ratio which was then evaluated. Thereflection density was measured at three density points, i.e., 1, 1.5and 2.0. The ozone gas concentration in the box was adjusted by the useof an ozone gas monitor (OZG-EM-01) produced by APPLICS CO., LTD.

The measurements were then evaluated according to the followingthree-step criterion. Those showing a dye remaining ratio of not smallerthan 80% at any density were ranked A. Those showing a dye remainingratio of less than 80% at one or two density points were ranked B. Thoseshowing a dye remaining ratio of less than 70% at all density pointswere ranked C.

The results thus obtained are set forth in Table 8. TABLE 8 PrintingPrinting properties properties Light- Heat Ozone Ink No. (1) (2)fastness fastness fastness 101 B B A D A (Comparative) 102 A A A A A(Inventive) 103 A A A A A (Inventive) 104 A A A A A (Inventive) 105 A AA A A (Inventive) 106 B B A D A (Comparative) 107 A A A A C(Comparative) 108 A A A A C (Comparative) 109 A A A A C (Comparative)110 B B A A C (Comparative)

From the results set forth in Table 8, the following facts were madeobvious.

The inks of the present invention have a good ejection stability and areexcellent all in weathering resistance (light-fastness, heat fastness,and ozone fastness), and their conductivity have a remarkable effect,particularly on heat fastness.

Example of viscosity change and surface tension change: Examples 5-6

Example 5

(Preparation of Ink Solution)

To the following components was added deionized water to make 1 l. Themixture was then heated to a temperature of from 30° C. to 40° C. withstirring for 1 hour. Thereafter, the solution was filtered through amicrofilter having an average pore diameter of 0.25 μm under reducedpressure to prepare a light cyan ink solution.

(Components of Light Cyan Ink Solution) Cyan dye of the presentinvention 17.5 g [Compound No. 154] Diethylene glycol 167 g Glycerin 164g Triethylene glycol monobutyl ether 125 g Triethanolamine 6.5 gBenzotriazole 0.07 g PROXEL XL2 [Zeneca Group Plc.] 3.5 g Surface activeagent (w-1) 10 g

Cyan, magenta, light magenta, cyan, yellow, dark yellow and black inkswere prepared in the same manner as used in the light cyan ink exceptthat the kind of dyes and the additives were changed. The ink set 101shown in Table 9 was thus prepared.

The viscosity of the ink was measured by means of a Type VM-100A-Lvibration viscometer (produced by YAMAICHI ELECTRONICS CO., LTD.).Further, the static surface tension of the ink was measured by means ofa Type CBVP-A3 automatic surface tensiometer (produced by KyowaInterface Science Co., LTD.). These measurements were then processedaccording to the aforementioned equations to calculate the change ofviscosity and surface tension from at 25° C. to at 10° C.

The temperature dependence of viscosity and surface tension of cyan andlight cyan inks of the ink set 101 are shown in FIGS. 1 and 2. TABLE 9Light Light Dark cyan Cyan magenta Magenta Yellow yellow Black Dye (g/l)154 154 A-1 A-1 A-3 A-3 A-5 17.5 68.0 10.2 30.8 14.0 10.0 20.0 A-4 A-4A-6 14.0 10.0 39.0 A-2 A-7 13.0 17.0 A-3 20.0 Diethylene 167 110 47 7685 — 20 glycol (g/l) Urea (g/l) — — 37 46 — — — Glycerin 164 148 198 150154 147 120 (g/l) Triethylene 125 132 105 107 130 127 — glycol monobutylether (g/l) Diethylene — — — — — — 230 glycol monobutyl ether (g/l)2-Pyrrolidone — 20 40 — — — 80 (g/l) Surface 10 10 6 12 3 3 5 activeagent (g/l) Triethanolamine 6.5 10 7 7 1 1 18 (g/l) Benzotriazole 0.070.09 0.07 0.08 0.06 0.08 0.08 (g/l) Proxel XL2 3.5 4.0 5.0 4.5 3 5 4(g/l) Change 180 190 188 183 188 192 ratio from 183 25 C. to 10 C.Viscosity 107 108 105 106 109 108 Surface 105 tensionDeionized water added to make 1 l

Subsequently, ink sets 102 to 106 were prepared in the same manner asdescribed above except that the kind of dyes in the light cyan and cyaninks of the ink set 101 were changed and the added amount of thewater-miscible organic solvent and surface active agent were changed tochange the change of viscosity and surface tension from at 25° C. to at10° C. as set forth in Table 10 below. TABLE 10 Change of static Changeof surface Ink set Dye viscosity tension Remarks 101 Light 154 180 107Inventive cyan 154 183 105 Cyan 102 Light 154 157 106 Inventive cyan 154155 108 Cyan 103 Light 108 177 107 Inventive cyan 108 169 106 Cyan 104Light 154 260 109 Comparative cyan 154 255 108 Cyan 105 Light 154 265135 Comparative cyan 154 262 132 Cyan 106 Light A-2 185 106 Comparativecyan A-2 183 107 Cyan(Ink jet recording)

The ink sets 101 to 107 thus prepared were each packed in the cartridgeof a Type PM920C ink jet printer (produced by EPSON CO., LTD.) by whichan image was then printed on a Type EX ink jet photographic gloss paper(produced by Fuji Photo Film Co., Ltd.) to evaluate the followingproperties. The results are set forth in Table 11.

(1) Printing Properties 1

For the evaluation of printing properties 1, the cartridge was mountedon the printer. The ejection of ink from all the nozzles was thenconfirmed. The printer was then allowed to stand in an atmosphere of 25°C. Printing was then made on 20 sheets of A4 size paper. The print wasthen evaluated for disturbance.

-   -   A: No print disturbance during the period between the beginning        and the end of printing;    -   B: Occurrence of output with print disturbance;    -   C: Print disturbance during the period between the beginning and        the end of printing.        (2) Printing Properties 2

For the evaluation of printing properties 2, the cartridge was allowedto stand at 10° C. for 2 days. The print was then evaluated fordisturbance in the same manner as in printing properties (1).

(3) Hue

The image was visually evaluated in the following manner.

-   -   G: Good level    -   F: Slightly poor level    -   P: Poor level.

For the evaluation of the following image preservability, yellow,magenta, cyan and black print samples were prepared. These samples werethen evaluated for the following properties.

(4) Light-Fastness

For the evaluation of light-fastness, the print which had been made wasimmediately measured for image density Ci by means of a reflectiondensitometer (X-Rite 310TR), irradiated with light from a xenon lamp(85,000 lux) using a weatherometer produced by Atlas Electric Devices,Inc. for 7 days, and then again measured for image density Cf todetermine the dye remaining ratio (Ci/Cf×100). The dye remaining ratiowas measured at three points of reflection density (1, 1.5, 2). Thoseshowing a dye remaining ratio of not smaller than 85% at any of thethree density points were defined as A, those showing a dye remainingratio of smaller than 85% at two of the three points were defined as B,and those showing a dye remaining ratio of smaller than 85% at all thethree density points were defined as C.

(5) Heat Fastness

For the evaluation of heat fastness, the sample was stored underconditions of from 70 to 80% RH for 7 days. The sample was measured fordensity using a reflection densitometer (Type X-rite 310TR) before andafter storage to determine the dye remaining ratio which was thenevaluated. The dye remaining ratio was then evaluated at threereflection density points, i.e., 1, 1.5 and 2. Those showing a dyeremaining ratio of not smaller than 90% at any of the three densitypoints were defined as A. Those showing a dye remaining ratio of lessthan 90% at two of the three density points were defined as B. Thoseshowing a dye remaining ratio of less than 90% at all the density pointswere defined as C.

(6) Ozone Resistance

For the evaluation of ozone resistance, the sample was stored under 80°C. heated conditions open to the atmosphere for 7 days. The sample wasmeasured for density using a reflection densitometer (Type X-rite 310TR)before and after storage to determine the dye remaining ratio which wasthen evaluated. The dye remaining ratio was then evaluated at threereflection density points, i.e., 1, 1.5 and 2. Those showing a dyeremaining ratio of not smaller than 90% at any of the three densitypoints were defined as A. Those showing a dye remaining ratio of lessthan 90% at two of the three density points were defined as B. Thoseshowing a dye remaining ratio of less than 90% at all the density pointswere defined as C.

The results thus obtained are set forth in Table 11. TABLE 11 InkPrinting Priting Light- Heat Ozone set properties 1 properties 2fastness fastness resistance Hue Remarks 101 A A A A A G Inventive 102 AA A A A G Inventive 103 A A A A A G Inventive 104 C B A A A GComparative 105 C B A A A G Comparative 106 A A B B C G Comparative

As can be seen in the results set forth in Table 11, when the inks ofthe present invention are used in ink jet recording, an excellentejection stability and an excellent fastness are given.

Even when the image-receiving paper to be used in the present inventionis changed to PM photographic gloss paper produced by EPSON Co., LTD. orPR101, produced by Canon Inc., effects similar to the aforementionedresults can be exerted.

Example 6

The inks prepared in Example 1 were each packed in the cartridge of aType BJ-F850 ink jet printer (produced by Canon Inc.) by which an imagewas then printed on a Type EX ink jet photographic gloss paper (producedby Fuji Photo Film Co., Ltd.) to effect evaluation in the same manner asin Example 1. Results similar to that of Example 1 were obtained. Evenwhen the image-receiving paper was changed to PM photographic glosspaper produced by EPSON CO., LTD. or PR101, produced by Canon Inc.,effects similar to the aforementioned results were exerted.

In accordance with the aforementioned example, an ink for ink jetrecording and an ink jet recording method which allow ejection with ahigh stability and give an image having an excellent hue andpreservability and a high quality can be provided.

Example of surface tension:

Example 7

(Preparation of Ink Solution)

To the following components was added deionized water to make 1.1. Themixture was then heated to a temperature of from 30° C. to 40° C. withstirring for 1 hour. Thereafter, the solution was filtered through amicrofilter having an average pore diameter of 0.25 μm under reducedpressure to prepare a light cyan ink solution.

(Components of Light Cyan Ink Solution) Cyan dye of the presentinvention 17.5 g [Compound No. 154] Triethylene glycol monobutyl ether119.0 g Glycerin 123.0 g Diethylene glycol 164.0 g Triethanolamine 6.5 gPROXEL XL2 [Zeneca Group Plc.] 1.0 g Benzotriazole 0.07 g2-Butyloctanoic acid ester terminated by 10.0 g polyethylene glycol(average number of repetition of ethylene oxide) at one end thereof

Magenta, light magenta, cyan, yellow, dark yellow and black inks werethen prepared in the same manner as described above except that amagenta dye (a-36), yellow dyes (A-3, A-4), and black dyes (A-5, A-6,A-7) were used as dyes instead of the cyan dye and the additives werechanged. These inks were then used to prepare an ink set 101 set forthin Table 12. TABLE 12 Light Light Dark magenta Magenta cyan Cyan Yellowyello Black Dye (g/l) (a-36) (a-36) (154) (154) A-3 A-3 A-5 10.2 30.817.5 68.0 14.7 10.3 20.0 A-4 A-4 A-6 14.0 9.8 39.0 (154) A-7 13.6 17.0A-3 20.0 Triethylene 130 140 119 127 130 130 — glcyol monobutyl ether(g/l) Diethylene — — — — — — 230 glycol monobutyl etehr (g/l) Glycerin(g/l) 130 160 123 110 150 138 120 Diethylene glycol 150 110 164 107 160144 20 (g/l) Triethanolamine 7 7 6.5 10 1 4 18 (g/l) Urea (g/l) 37 46 —— — — — 2-Pyrrolidone 40 — — 20 — — 80 (g/l) PROXEL XL II 5.0 4.5 1.04.0 3.0 3.0 4.0 (g/l) Benzotriazole 0.07 0.08 0.07 0.09 0.06 0.07 0.08(g/l) 2-Butyloctanoic 6 12 10 10 3 5 5 acid ester terminated bypolyethyelne glycol at one end (g/l) a-36

R¹, R²:

R³, R⁴:

Subsequently, ink sets 102 to 107 were in the same manner as describedabove except that the kind of dyes, the amount of surface active agentwhich is a surface tension adjustor and the kind and amount of organicsolvents in the light cyan and cyan inks of the ink set 101 were changedas set forth in Table 13 below. The static surface tension of these inkswas measured by means of a Type CBVP-A3 automatic surface tensiometer(produced by Kyowa Interface Science Co., LTD.) Further, the dynamicsurface tension of these inks was measured by means of a Type BP-D3automatic surface tensiometer (produced by Kyowa Interface Science Co.,LTD.)

The unit of the amount of the various solvents in Table 13 is g/l. TABLE13 Static Dynamic surface surface Static Dynamic tension tension surfacesurface Ink Light Light Light tension tension set Cyan Cyan cyan cyanCyan Cyan Remarks 101 Dye (154) (154) 32.5 33.9 32.6 33.4 InventiveSurface active 10 10 mN/m mN/m mN/m mN/m agent Diethylene glycol 164 107Glycerin 123 110 Triethylene 119 127 glycol monobutyl ether 102 Dye(154) (154) 32.9 34.9 32.4 33.3 Inventive Surface active 10 10 agentDiethylene glycol 30 35 Glycerin 5 8 Triethylene 50 47 glycol monobutylether 103 Dye (154) (154) 33.1 35.2 32.0 32.5 Inventive Surface active10 10 agent Diethylene 30 35 glycol Glycerin 5 8 Triethylene — — glycolmonobutyl ether 104 Dye (154) (154) 36.7 37.8 37.4 37.4 InventiveSurface active 10 10 agent Diethylene 150 110 glycol Glycerin 130 130Triethylene 130 140 glycol monobutyl ether 105 Dye (154) (154) 51.2 50.451.5 50.7 Comparative Surface active — — agent Diethylene 30 35 glycolGlycerin 5 8 Triethylene — — glycol monobutyl ether 106 Dye (154) (154)23.4 23.9 23.7 23.7 Comparative Surface active 10 10 agent Diethylene150 110 glycol Glycerin 130 130 Triethylene 160 170 glycol monobutylether 107 Dye (191) (191) 32.2 33.6 32.0 32.8 Comparative Surface active10 10 agent Diethylene 164 107 glycol Glycerin 123 110 Triethylene 119127 glycol monobutyl ether (191)

(Ink Jet Recording)

The ink sets 101 to 107 thus prepared were each packed in the cartridgeof a Type PM920C ink jet printer (produced by EPSON Co., LTD.) by whichan image was then printed on a Type EX ink jet photographic gloss paper(produced by Fuji Photo Film Co., Ltd.) to evaluate the followingproperties. The results are set forth in Tables 14 and 15.

(1) Printing Properties (1)

For the evaluation of printing properties (1), the cartridge was mountedon the printer. The ejection of ink from all the nozzles was thenconfirmed. Printing was then made on 20 sheets of A4 size paper. Theprint was then evaluated for disturbance.

-   -   A: No print disturbance during the period between the beginning        and the end of printing;    -   B: Occurrence of output with print disturbance;    -   C: Print disturbance during the period between the beginning and        the end of printing;        (2) Printing Properties (2)

For the evaluation of printing properties (2), the cartridge was allowedto stand at 60° C. for 2 days. The print was then evaluated fordisturbance in the same manner as in printing properties (1).

(3) Dryability

For the evaluation of dryability, the print was immediately touched witha finger which was then visually observed for stain.

(4) Running of Fine Line (1)

Fine line patterns were printed with yellow, magenta, cyan and blackinks, respectively. These fine line patterns were each then visuallyevaluated for “running of fine line (1)”.

-   -   G: Good    -   F: Slight running    -   P: Running.        (5) Running of Fine Line (2)

A fine line was printed with a black ink on a solid print of cyan ink.The fine line was then evaluated for running of fine line due to contactof two color inks.

(6) Water Resistance

The image thus obtained was dipped in deionized water for 5 seconds, andthen evaluated for running.

For the evaluation of image preservability, yellow, magenta, cyan andblack print samples were prepared. These samples were then evaluated asfollows.

(7) Light-Fastness

For the evaluation of light-fastness, the print which had been made wasimmediately measured for image density Ci by means of X-Rite 310,irradiated with light from a xenon lamp (85,000 lux) using aweatherometer produced by Atlas Electric Devices, Inc. for 6 days, andthen again measured for image density Cf to determine the dye remainingratio [Cf/Ci]×100. The dye remaining ratio was measured at three pointsof reflection density (1, 1.5, 2). Those showing a dye remaining ratioof not smaller than 80% at any of the three density points were definedas A, those showing a dye remaining ratio of smaller than 80% at two ofthe three points were defined as B, and those showing a dye remainingratio of smaller than 80% at all the three density points were definedas C.

(2) Moist Heat Fastness

For the evaluation of heat fastness, the sample was stored underconditions of 70 to 80% RH for 5 days. The sample was measured fordensity using X-rite 310 before and after storage to determine the dyeremaining ratio which was then evaluated. The dye remaining ratio wasthen evaluated at three reflection density points, i.e., 1, 1.5 and 2.Those showing a dye remaining ratio of not smaller than 90% at any ofthe three density points were defined as A. Those showing a dyeremaining ratio of less than 90% at two of the three density points weredefined as B. Those showing a dye remaining ratio of less than 90% atall the density points were defined as C. TABLE 14 Ink Printing PrintingRunning of Running of Water set properties 1 properties 2 Dryabilityfine line 1 fine line 2 resistance 101 A A G G G G (good) 102 A A G G GG 103 A A G G G G 104 A A G F F G 105 B C G P P G 106 C C G P P G 107 AA G G G G

TABLE 15 Ink Light fastness Moist heat fastness set Yellow Magenta CyanBlack Yellow Magenta Cyan Black 101 A A A A A A A A 102 A A A A A A A A103 A A A A A A A A 104 A A A A A A A A 105 A A A A A A A A 106 A A A AA A A A 107 A A B A A A A A

From the results set forth in Tables 14 and 15, the following facts aremade obvious.

When the inks of the present invention are used in ink jet recording, anexcellent ejection stability can be obtained. The image thus recordedexhibits excellent properties in water resistance and fastness. Further,when the inks of the present invention are used, fine lines free ofrunning can be outputted, making it possible to obtain an excellentimage.

Even when the image-receiving paper to be used in the present inventionwas changed to PM photographic gloss paper produced by EPSON CO., LTD.or PR101, produced by Canon Inc., effects similar to the aforementionedresults were exerted.

In accordance with the aforementioned example, an ink for ink jetrecording and an ink jet recording method which allow ejection with ahigh stability and give an image having an excellent hue andpreservability (weathering resistance, water resistance) and a highquality can be provided.

Example of ultrasonic vibration:

Example 8

(Preparation of Ink Solution)

To 17.5 g of a cyan dye [154] was added 150 cc of deionized water. Thedye was then stirred with the application of ultrasonic vibration usingan ultrasonic cleaner (2510J-DTH, produced by BRANSON, 43 kHz, 125 W)for 10 minutes to undergo dissolution (first step). To the dye solutionwere then added the following components. To the dye solution was thenadded deionized water to make 1 l. The dye solution was then heated to atemperature of from 30° C. to 40° C. with stirring for 1 hour (secondstep). The mixture was then filtered through a microfilter having anaverage pore diameter of 0.25 μm under reduced pressure to prepare alight cyan ink solution. Triethylene glycol monobutyl ether 119.0 gGlycerin 123.0 g Diethylene glycol 164.0 g Triethanolamine 6.5 g PROXELXL2 [Zeneca Group Plc.] 1.0 g Benzotriazole 0.07 g Surface active agent(2-Butyloctanoic 6.0 g acid ester terminated by polyethylene glycol(average number of repetition of ethylene oxide) at one end thereof)

To 68.0 g of a cyan dye [154] was added 500 cc of deionized water. Thedye was then stirred with the application of ultrasonic vibration usingthe aforementioned ultrasonic cleaner for 10 minutes to undergodissolution. To the dye solution were then added the followingcomponents. To the dye solution was then added deionized water to make 1l. The dye solution was then heated to a temperature of from 30° C. to40° C. with stirring for 1 hour. The mixture was then filtered through amicrofilter having an average pore diameter of 0.25 μm under reducedpressure to prepare a light cyan ink solution. Triethylene glycolmonobutyl ether 127.0 g Glycerin 110.0 g Diethylene glycol 107.0 gTriethanolamine 10.0 g PROXEL XL2 [Zeneca Group Plc.] 4.0 gBenzotriazole 0.09 g Surface active agent (2-Butyloctanoic 10.0 g acidester terminated by polyethylene glycol (average number of repetition ofethylene oxide) at one end thereof)

Example 9

Light cyan and cyan ink solutions were prepared in the same manner as inExample 1 except that the addition of deionized water to the cyan dyefollowed by dissolution with stirring for 1 hour was not assisted byultrasonic vibration and the addition of the remaining components to theaqueous solution of dye followed by heating to a temperature of from 30°C. to 40° C. with stirring for 30 minutes was assisted by ultrasonicvibration.

Comparative Example 1

Light cyan and cyan ink solutions were prepared in the same manner as inExample 8 except that as the cyan dye there was used (C-1).

Comparative Example 2

Light cyan and cyan ink solutions were prepared in the same manner as inExample 8 except that the preparation of the ink solution was notassisted by ultrasonic vibration at all.

Example 10

Ink solutions were prepared in the same manner as in Comparative Example2. Using an ultrasonic cleaner, ultrasonic vibration was then applied tothese ink solutions to prepare light cyan and cyan ink solutions.

(Ink Jet Recording)

The light cyan and cyan inks thus prepared were each packed in thecartridge of a Type PM920C ink jet printer (produced by EPSON CO., LTD.)by which an image was then printed on a Type EX ink jet photographicgloss paper (produced by Fuji Photo Film Co., Ltd.) to evaluate thefollowing properties. The results are set forth in Table 16.

(1) For the evaluation of ejection stability, the cartridge was mountedon the printer by which the ink was then subjected to continuousejection test through nozzles.

-   -   G: Stable    -   F: Slightly stable    -   P: Unstable.        (2) For the evaluation of image preservability, a solid cyan        image print sample was prepared. The sample was then evaluated        for the following properties.

For the evaluation of light-fastness, the print which had been made wasimmediately measured for image density Ci by means of a reflectiondensitometer (X-Rite 310TR), irradiated with light from a xenon lamp(85,000 lux) using a weatherometer produced by Atlas Electric Devices,Inc. for 6 days, and then again measured for image density Cf todetermine the dye remaining ratio (100×Cf/Ci). The dye remaining ratiowas measured at three points of reflection density (1, 1.5, 2). Thoseshowing a dye remaining ratio of not smaller than 80% at any of thethree density points were defined as A, those showing a dye remainingratio of smaller than 80% at two of the three points were defined as B,and those showing a dye remaining ratio of smaller than 80% at all thethree density points were defined as C.

For the evaluation of heat fastness, the sample was stored underconditions of 80° C. and 70% RH for 5 days. The sample was measured fordensity using a reflection densitometer (Type X-rite 310TR) before andafter storage to determine the dye remaining ratio which was thenevaluated. The dye remaining ratio was then evaluated at threereflection density points, i.e., 1, 1.5 and 2. Those showing a dyeremaining ratio of not smaller than 90% at any of the three densitypoints were defined as A. Those showing a dye remaining ratio of lessthan 90% at two of the three density points were defined as B. Thoseshowing a dye remaining ratio of less than 90% at all the density pointswere defined as C.

For the evaluation of ozone resistance, the sample was stored under 80°C. heated conditions open to the atmosphere for 7 days. The sample wasmeasured for density using a reflection densitometer (Type X-rite 310TR)before and after storage to determine the dye remaining ratio which wasthen evaluated. The dye remaining ratio was then evaluated at threereflection density points, i.e., 1, 1.5 and 2. Those showing a dyeremaining ratio of not smaller than 90% at any of the three densitypoints were defined as A. Those showing a dye remaining ratio of lessthan 90% at two of the three density points were defined as B. Thoseshowing a dye remaining ratio of less than 90% at all the density pointswere defined as C. TABLE 16 Ultrasonic Ejection Light- Heat Ozone InkDye vibration stability fastness fastness resistance Example 8 (154)Applied at G A A A first step Example 9 (154) Applied at G A A A secondstep Comparative (C-1) Applied at G C A C Example 1 first stepComparative (154) Not applied P A A A Example 2 Example 10 (154) Appliedafter F A A A preparation of ink

It is made obvious that when the inks obtained according to the presentinvention are used, an excellent ejection stability can be obtained. Itis also made obvious that the inks of the present invention exhibitexcellent properties in fastness as well.

Further, the inks of the present invention exhibited hues similar tothat of Comparative Example 1.

Moreover, inks of the present invention prepared in the same manner asin the aforementioned example except that other water-soluble dyesrepresented by the formula (I) were used instead of the cyan dye (154)had the same effect on weathering resistance, ejection stability and hueas in the aforementioned example.

Even when the image-receiving paper was changed to PM photographic glosspaper produced by EPSON CO., LTD. or PR101, produced by Canon Inc.,effects similar to the aforementioned results were exerted.

In accordance with the aforementioned example, an ink set for ink jetrecording comprising an aqueous ink advantageous in handleability, odor,safety, etc. which allows ejection with a high stability and gives arecorded image having a good hue and an excellent weathering resistanceand water resistance and good running of fine line can be provided.

Example of filtration and defoaming:

Example 11

(Preparation of Ink Solution)

To the following components was added deionized water to make 1 l. Themixture was then heated to a temperature of from 30° C. to 40° C. withstirring for 1 hour. Thus, a light cyan ink solution (LC-101) wasprepared.

[Formulation of Light Cyan Ink LC-101]

(Solid Content) Cyan dye of the present invention (154) 17.5 g/l PROXEL3.5 g/l

(Liquid Content) Diethylene glycol 150 g/l Glycerin 130 g/l Triethyleneglycol monobutyl ether 130 g/l [Triethanolamine] 6.9 g/l Surfynol STG 10g/l Triethanolamine (TEA) 6.9 g/l Surfynol STG (SW) 10 g/l

A cyan ink solution C-101 was then prepared according to theaforementioned formulation except that the added amount of the cyan dye(154) was raised to 68 g.

[Formulation of Light Cyan Ink C-101]

(Solid Content) Cyan dye of the present invention (154) 68 g/l PROXEL3.5 g/l

(Liquid Content) Diethylene glycol 150 g/l Glycerin 130 g/l Triethyleneglycol monobutyl ether 130 g/l Triethanolamine 6.9 g/l Surfynol STG 10g/l

These inks thus prepared were each filtered through a filter, and thensubjected to defoaming using an ultrasonic defoamer for 10 minutes.

Thereafter, these inks were packed in the cyan ink and light cyan inkcartridges of a Type PM-950C ink jet printer (produced by EPSON CO.,LTD.), respectively. As the other color inks there were used the inksdedicated to PM-950C. A chromatic magenta image was then printed. Theimage was printed on a Type EX ink jet photographic gloss paper(produced by Fuji Photo Film Co., Ltd.) as an image-receiving sheet.Thus, ejection stability was evaluated.

The packing of ink was effected in the same manner as described aboveexcept that the step of filtering through a filter, the step ofperforming defoaming by means of an ultrasonic defoamer for 10 minutesand the cleanness of the step were changed as set forth in Table 17below. TABLE 17 Experiment Filter Ultrasonically No. Filtered ? diameterdefoamed ? cleanness* 101 (comparative) No — No 100,000 102(comparative) Yes 250 nm No 100,000 103 (inventive) Yes 250 nm Yes100,000 104 (comparative) Yes 50,000 nm Yes 100,000 105 (comparative)Yes 50,000 nm No 800 106 (comparative) Yes 250 nm No 800 107 (inventive)Yes 50,000 nm Yes 800 108 (inventive) Yes 250 nm Yes 800 109 (inventive)Yes 100 nm Yes 800 110 (inventive) Yes 500 nm Yes 800*Cleanness indicates a value measured by a duster counter

The evaluation of ejectability was effected as follows.

(Evaluation Experiment)

For the evaluation of ejection stability, the cartridge was mounted onthe printer. The ejection of the inks from all the nozzles was thenconfirmed. Printing was then made on 100 sheets of A4 size paper.Evaluation was made according to the following criterion.

-   -   A: No print disturbance during the period between the beginning        and the end of printing;    -   B: Occurrence of output with print disturbance;    -   C: Print disturbance during the period between the beginning and        the end of printing.

The results thus obtained were set forth in Table 18. TABLE 18Experiment No. Ejection stability 101 (Comparative) C 102 (Comparative)B 103 (Inventive) B 104 (Comparative) C 105 (Comparative) B 106(Comparative) B 107 (Comparative) B 108 (Inventive) A 109 (Inventive) A110 (Inventive) A

As can be seen in the results of Table 18, the systems 103 and 108 to110, which comprise inks prepared according to the process of thepresent invention, exhibit a good ejection stability. In particular,when filtration and defoaming are effected in a space having a cleannessof not greater than 1,000, the ejection stability of the ink can beenhanced.

(Advantage of the Present Invention)

In accordance with the present invention, an ink for ink jet recordingcomprising an aqueous ink advantageous in handleability, odor, safety,etc. which allows ejection with a high stability and gives a highquality recorded image having a good hue and an excellent weatheringresistance and water resistance, a process for the production thereofand an ink jet recording process can be provided.

Industrial Applicability

The ink jet recording process to which the ink of the present inventionis applied is not limited. The ink set of the present invention may beused in any known recording process such as electrostatic control methodwhich utilizes electrostatic attraction to eject ink, drop-on-demandmethod (pressure pulse method) utilizing vibrational pressure ofpiezoelectric element, acoustic ink jet method which comprisesconverting electrical signal to acoustic beam with which the ink isirradiated to produce a radiation pressure that is utilized to eject theink and thermal ink jet (bubble jet) method which comprises heating theink to form bubbles that raise the pressure to eject the ink.

Examples of the ink jet recording process include a process whichcomprises ejecting many portions of an ink having a low concentrationcalled photoink in a small volume, a process which comprises using aplurality of inks having substantially the same hue but differentdensities to improve the image quality, and a process involving the useof a colorless transparent ink.

1. An ink for ink jet recording, comprising a aqueous medium and aphthalocyanine dye dissolved or dispersed in the aqueous medium, whereinthe phthalocyanine dye has an oxidation potential of more positive than1.0 V and the ink has a conductivity of 0.01 S/m to 10 S/m.
 2. The inkfor ink jet recording according to claim 1, which has a viscosity of 1to 20 mPa·sec at 25° C.
 3. The ink for ink jet recording according toclaim 1, which has a static surface tension of 25 to 50 mN/m at 25° C.4. The ink for ink jet recording according to claim 2, wherein aviscosity of the ink has a viscosity ratio of not greater than 250% fromat 25° C. to at 10° C., and a static surface tension has a staticsurface tension ratio of not greater than 130% from at 25° C. to at 10°C.
 5. The ink for ink jet recording according to claim 1, which has a pHvalue of 4 to 12 at 25° C.
 6. The ink for ink jet recording according toclaim 1, which has a dye remaining ratio of not smaller than 60% after24 hours of storage in an atmosphere of 5 ppm ozone in a monochromaticarea that is obtained by printing with a monochromatic ink in such amanner a cyan reflection density through a status A filer is from 0.9 to1.1.
 7. The ink for ink jet recording according to claim 1, wherein theink has Cu ions that are eluted with water in an amount of not greaterthan 20% of a total amount of the dye after an ozone fading under theconditions defined in claim
 6. 8. The ink for ink jet recordingaccording to claim 1, wherein the phthalocyanine dye is a water-solubledye having an electron-withdrawing group at β-position of a benzene ringin the phthalocyanine.
 9. The ink for ink jet recording according toclaim 1, wherein the phthalocyanine dye is a water-soluble dye that isproduced by a process which doesn't pass through a sulfonation of anunsubstituted phthalocyanine.
 10. The ink for ink jet recordingaccording to claim 1, wherein the phthalocyanine dye is represented bythe following formula (I):

wherein X₁, X₂, X₃ and X₄ each independently represent —SO-Z, —SO₂-Z,—SO₂NR₁R₂, sulfo group, —CONR₁R₂ or —CO₂R₁; Z represents a substitutedor unsubstituted alkyl group, substituted or unsubstituted cycloalkylgroup, substituted or unsubstituted alkenyl group, substituted orunsubstituted aralkyl group, substituted or unsubstituted aryl group orsubstituted or unsubstituted heterocyclic group; R₁ and R₂ eachindependently represent a hydrogen atom, substituted or unsubstitutedalkyl group, substituted or unsubstituted cycloalkyl group, substitutedor unsubstituted alkenyl group, substituted or unsubstituted aralkylgroup; substituted or unsubstituted aryl group or substituted orunsubstituted heterocyclic group; and when there are a plurality of Z's,they may be the same or different; Y₁, Y₂, Y₃ and Y₄ each independentlyrepresent a monovalent substituent; and when there are a plurality ofany of X₁ to X₄ and Y_(1 to Y) ₄, they may be the same or different; a₁to a₄ and b₁ to b₄ represent the number of substituents X₁ to X₄ andY_(1 to Y) ₄, respectively; a₁ to a₄ each independently represent aninteger of from 0 to 4 and are not 0 at the same time; and b₁ to b₄ eachindependently represent an integer of 0 to 4; and M represents ahydrogen atom, metal atom or oxide, hydroxide or halide thereof.
 11. Theink for ink jet recording according to claim 10, wherein the dyerepresented by the formula (I) is a dye represented by the followingformula (II):

wherein X₁₁ to X₁₄, Y₁₁ to Y₁₈ and M each have the same meaning as thosein the formula (I); and a₁₁ to a₁₄ each independently represent aninteger of 1 or
 2. 12. A method for ink jet recording, comprising usingthe ink for ink jet recording according to claim
 1. 13. A method forrecording an image on an image-receiving material, comprising ejectingan ink droplet onto the image-receiving material including animage-receiving layer containing an inorganic white particulate pigmenton a support according to a record signal, wherein the ink dropletcomprises the ink for ink jet recording according to claim
 1. 14. Amethod for producing the ink for ink jet recording according to claim 1,which comprises at least applying an ultrasonic vibration.
 15. A methodfor producing the ink for ink jet recording according to claim 1,wherein the ink for ink jet recording prepared is filtered through afilter having pores of an effective diameter of not greater than 1 μmand defoamed before use.